Phoenix:
Hi Kjandtj35,
I should mention first of all that all of this is more a matter of knowing the tradeoffs rather than any particular material being a “mistake”. If a 4 lb density memory foam or gel memory foam is the density that provides the feel, comfort, and support that someone wants, then it may still be the best choice for that person as long as they know they may be trading the feel they want for durability.
In general … higher densities of any foam will be more durable than lower densities and this is fairly progressive with memory foam until you get into the 5 or 6 lb range at which point the relative durability benefits of higher densities start to level off.
So with heavier weights I would look for memory foam in the 5 lb and higher range. the tradeoff for this though is that they tend to feel firmer to people … especially if their weight is lighter.
Memory foam is also a little tricky because how soft it feels is dependent on many factors including the force applied to it, humidity, temperature, and time. Fast response foams tend to respond mainly to the force applied. What this means for example is that memory foam that has warmed up under the heat of the body for a while will feel softer than memory foam that is a little cooler when you first lie on it so if you roll over and change positions, the foam beside you that you are moving into will feel firmer while the foam under you will feel softer. The density of memory foam is also not directly related to firmness and softness so lower density memory foam can be firmer than higher density memory foam depending on the chemical formulation used. Two different types of memory foam that have the same density will be roughly comparable in durability terms in other words but can feel very different from each other depending on the chemical formula used to make them. As a generic guideline though … 4 lb memory foam will feel softer overall to most people than 5 lb memory foam. You can read more about all the different varieties of memory foam in post #9 here and in post #8 here .
All of this can be quite complex and “overwhelming” though when there are so many factors to consider and the simplest way is to use foam density and thickness as your guideline along with how your body feels on different mattresses that use various densities of memory foam which can give you a rough guideline. I would suggest testing Tempurpedic mattresses that include their higher density memory foam in the Contour collection (Rhapsody, Allura, Grand Bed) to see how “soft” higher density memory foam (that is "broken in) feels to both of you as well as their weightless collection which includes thinner layers of lower density memory foam over more resilient foam. The less lower density memory foam there is in the upper layers and the more durable the foam below it is the less foam softening will affect you. In other words … if you must have 4 lb memory foam in the top layers because of how it feels for your wife (lighter weights sink in less so foams that feel soft to you may feel firmer to her) … the less of it the better in terms of durability.
One other advantage you may have is that your previous mattresses lasted for longer than would often be typical for your weight (again this would depend on what was in the mattresses which I don’t know) but this may point to you being less sensitive to foam softening and the loss of comfort and support that goes with it than other people of your height and weight so for you a mattress that uses less durable materials may last a little longer than the “norm” for your height and weight.
Everything is a tradeoff and there is nothing “wrong” with trading durability for comfort. There is also nothing “wrong” with trading support (less sinking in) for its opposite which is comfort (more sinking in) as long as you are still in your acceptable range for both (comfort issues tend to be related to pressure points while support issues tend to be related to spinal alignment and back pain). A mattress that is supportive for a lighter weight may not be supportive enough for a heavier weight and allow some of the heavier parts of the body to sink in too far and cause alignment issues and back pain. finding the balance between the two of you is part of the challenge.
Some mattresses even have side to side “splits” or other designs that can accommodate weight differences between couples more effectively (see post #2 here ). All of this is why it can be very helpful to deal with a mattress retailer or manufacturer who is very knowledgeable about mattress construction and materials and how to “fit” the needs and preferences of different types of people so they can help and guide you into making the most suitable choices for both of you no matter what is most important to you. How well you sleep can be just as important for many people as how long a mattress lasts or any other tradeoff … as long as you are making tradeoffs knowingly by choice rather than being “surprised” in a few years down the road when a mattress using lower density materials don’t last as long as a similar mattress that uses higher density and more durable materials.
Phoenix
Ok I am starting to understand better how the foam and density’s work vs the trade off of comfort and durability. I took your advice tried out the higher density beds you mentioned, the one both me and my wife like was the rhapsody breeze. Can you tell me about the construction of this bed and if any of the competitors such as Brooklyn beds or other have duplicated the build with success? I seen select foam seems to have a marketing of comparing theirs skus to temperpedic skus. I know nothing about select foam though and theirs prices seem to be a little higher then other competitors I did see they use a 8lb density? The largest I have seen was 5lb.