Hi sndslpr,
Your post is a great chance to expand on some of the most common frustrations (at least for me and I know many others) in the mattress industry and one of the reasons I make some of the suggestions that I do.
There are really 3 stages or processes of foam “breakdown”. The first stage is often referred to as the break in period. This is the initial 90 days or so when most polyfoam or memory foam will soften more rapidly. The lower the quality of foam (measured by density) … the more this will happen.
The second stage of foam breakdown is the more gradual softening that happens after this. Once again … the lower the quality of the foam the faster this will happen.
The last stage of foam breakdown is when it actually starts to form deeper impressions and starts to break down and degrade. Once again … the lower the quality of foam (or the higher the weight of the people on the mattress) the faster this will happen even though this is a longer term process.
Warranties don’t cover the first two because they have what are called “exclusions” and a warranty claim will only be honored if the actual impression when someone is off the mattress is deeper than the exclusion (in many cases 1.5" but sometimes .75" with better quality memory foam or latex). Polyfoam and memory foam will still have enough resiliency left to come back “close to level” long after the softening process (stage 1 and 2) has made the mattress unsuitable for sleeping.
This is also one of the reasons I like good quality latex because the initial softening is much less than other foams, the more gradual softening process takes much longer, and the breakdown takes even longer yet. While all foam that is used in the upper layers of a mattress will go through these three processes … good quality latex will last much longer for every stage (although all foam materials have higher quality more durable versions and lower quality less durable versions).
Almost all of the major manufacturers use several inches of lower density soft polyfoam (or a fiber that will compress) in their mattress and the thicker these layers are and the closer to the top of the mattress they are … the more they are likely to become the weak link of the mattress. A mattress with say 2" of low quality/density foam or more near the top will greatly increase the odds that the mattress will lose the properties that make it suitable for a particular individual even though all the rest of the foam and the innersprings are still in good shape. In those few cases where these major manufacturers don’t have the lower quality foam in their mattress … the prices are often much higher than a similar quality mattress bought from a local manufacturer.
When a foam softens … if you put a high quality topper on top of it … the softened layers become the support layers for the topper over it and the topper will follow the soft spots or any sagging in the mattress when there is weight on it which is why it is much more difficult to try and “fix” a mattress that has softened in a particular area (usually the heavier areas of the body such as the hips and pelvic area) or where the comfort layers were too soft or thick initially by adding a topper. At best a firmer topper may provide a partial or temporary solution and at worst it could make things worse (it could make the top layer you are sleeping on too firm in terms of “comfort” and pressure relief and the layers underneath it may still be too soft to provide good support/alignment under the topper). Support comes primarily from the deeper layers of the mattress and while adding a topper can help with pressure relief and “fix” a mattress that is too firm … it will only have a minimal to small and likely temporary effect on the support properties of the mattress (see post #4 here as well)
Turning a mattress (more often in the beginning and then less frequently) or even better yet flipping it as well (for a 2 sided mattress which most major manufacturers don’t make any more) can significantly delay these processes but won’t stop them. This is often another advantage to buying a mattress from a local manufacturer because many of them will fix an issue like this if it becomes necessary by replacing the problem layer for a very reasonable charge.
6-7 years is well within the range where any lower quality foam will have softened enough to cause the types of issues you are having with your mattress … and it’s often much less. This is called “built in obsolescence”, is done by intent IMO, and is not covered by warranty because of the exclusions I mentioned earlier in this post. The heavier a person is and the more mechanical stress that their sleeping habits create on the upper layers of a mattress … the faster these processes will occur.
Some of the options to check or that may help if a mattress becomes less supportive because of the softening or breakdown of materials (or was too soft originally) include …
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Check the foundation of your mattress to make sure the loss or lack of support is in the mattress itself and not in the foundation (where the mattress is following a dip in the foundation or innerspring under the mattress). The same holds true for the bed or frame that the foundation is resting on. You can test this by putting the mattress on the floor as well to see if it has the same issues.
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A product such as the Mattress Remedy or the Mattress Helper (check google for best pricing) or zzzboard placed under the mattress in the area of the sag may provide some help. This is not a perfect solution and can have varying degrees of success depending on circumstances but if it works to provide the extra support you need in the area you need it, it can at least allow you to keep your mattress for a while longer. EDIT: The mattress remedy is no longer available as they have “lost the patent” but they may be working on something similar so I’ve left it here so that those who read this can check.
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Thick folded blankets, layers of felted carpet padding, or layers of firmer foam placed under the middle third of your mattress in the area of the sag may give you enough “extra” support in the areas that are sagging similar to #2 to extend the life of your mattress. 1x3" or 1x4" wooden slats placed over your current slats or foundation under the area of the body that needs extra support or to be “lifted” (typically under the pelvis, the lumbar arch, or both) can also provide some extra support under specific areas of the body that may be sinking down or sagging too much and help with alignment You can see an example from one of the members here with some pictures in post #9 here and there are also some suggestions in post #11 here about zoning that may be helpful as well.
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A product such as a night roll described in the video here may help to provide better support for the recessed areas of the body (such as the waist or small of the back) and may provide better spinal alignment on a mattress that is either too soft or that has developed soft spots or visible impressions and would be well worth a try.
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Even though the bottom of a one sided mattress isn’t really designed for sleeping on and is meant to provide very firm support over a foundation … it may be worth trying to turn the mattress over and using a topper to add a comfort layer on top of the firmer bottom side. This may or may not work depending on the thickness and softness of the layers that are now on the bottom and whether they are too thick and soft to provide good alignment and support but it would probably be worth risking the price of a good quality topper (and there is less risk if the topper can be returned or exchanged for a different firmness level) instead of replacing the mattress. If you choose to go in this direction there is more information in post #2 here and the topper guidelines it links to in post #8 here that would be helpful. Since there is usually little give or contouring on the bottom of a mattress to act as a transition layer between the softer top layer (topper) and the firmer support layer of the mattress I would probably lean towards a topper in the 3" - 4" range.
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If you have a memory foam mattress then adding a topper or a “zoning material” on top of the mattress can reduce the amount of body heat that reaches the memory foam and can help keep it firmer or slow down the time it takes to become softer over the course of the night which can have some effect on improving the firmness and support of the memory foam under the heavier parts of the body which may be “just enough” to make a difference … at least for a while (see this topic)
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Turning down the thermostat in your bedroom so you have a cooler sleeping environment may firm up memory foam somewhat or once again slow down the length of time it takes to become softer over the course of the night.
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Rebuilding your mattress. This would be possible if there is a local manufacturer near you that is willing to do this and can replace any failing layers or layers that are too thick or soft with better quality materials or build a more suitable design using some of the old layers or components and then close up the mattress again so in effect you have an “almost new” mattress with a professional “finished” appearance at a much lower cost than replacing the whole mattress. In the case of a component mattress with a zip cover of course then you could replace individual layers.
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Mattress Surgery. This can be a last resort when there are no other reasonable options. This involves cutting open the mattress … removing the layers of foam inside that either are or will cause problems … and then replacing them with higher quality foam over the innersprings or other mattress support layers (which will almost certainly still be fine). The current mattress ticking can either be re-used (either re-sewn or velcroed back together) or a zipper mattress ticking that fits the thickness of your “new” mattress can be used. While this can certainly be fun, it can also be intimidating and challenging (and can be difficult to remove foam in some mattresses if the layers are glued together) and would involve some research into what foams you would use to replace the ones you have. There is more about mattress surgery in post #2 here.
So outside of removing and replacing layers that are either sagging or are too soft there are really no great options to fix a sagging mattress, a mattress that was too soft initially, or a mattress that has developed soft spots but there are at least lower cost ways that might be worth trying that may help enough to extend the life of what you have. The real issue is that these types of mattresses are so common in the industry today … even in the higher budget “premium” mattresses … and that so many people are facing the same issues as you are, many of them after even less time than yours.
Phoenix