Hi lilmom,
There are many reasons why so many manufacturers in the industry use layers or components that are more likely to be a weak link in the mattress. In most cases it’s because they believe that they will sell more mattresses at a lower cost and/or higher profit than they would if they used higher quality and more durable materials which resulted in a mattress that has a higher price (in which case they could sell less) or a lower profit.
The vast majority of consumers tend to buy a mattress based on the more subjective “showroom feel” or “comfort” of a mattress and pay very little attention to more objective testing and whether a mattress keeps them in good alignment or the durability of the materials because unlike you they aren’t very knowledgeable about mattresses and mattress materials and just don’t know any better. A thicker quilting layer that uses lower density foam will also reduce the surface resilience of the latex and can result in a softer more “cushy” feel which is “attractive” to many consumers and which can lead to more mattress sales at a lower cost even though it can also be more risky in terms of durability and alignment.
Thicker layers of lower density and less durable materials (particularly in the top layers of a mattress) can result in premature foam softening and the more rapid loss of comfort and support in a mattress even if there aren’t any significant visible impressions in the mattress so even though the mattress wouldn’t be “lumpy” … if foam softening takes you outside the comfort/support range that is suitable for a particular person and they are no longer sleeping well because they are sleeping out of alignment over the course of the night then they would need to replace the mattress more quickly.
I would also keep in mind that the more rapid foam softening that you can expect with thicker layers of lower quality/density materials isn’t covered by mattress warranties which only covers manufacturing defects and visible impressions in the mattress that are deeper than the warranty exclusions (when nobody is on the mattress) and visible impressions that are deeper than the warranty exclusion is less likely to happen with only 2" of lower density foam so there would be little risk of a successful warranty claim and the manufacturers know this. It can also work in their favor if consumers need to replace their mattresses more quickly so part of the reason is “because they can” and there is little risk from the perspective of the manufacturer.
There is more about mattress warranties in post #174 here and as you can see the length of a warranty has little to do with the durability and useful life of a mattress and how long it will be before you need to replace it.
While there is no way to specifically quantify how long any mattress will last for a specific person or predict exactly when they will decide to replace it because it is no longer suitable or comfortable for them (because this is the only real measure of durability or the useful life of a mattress that really matters) and because there are too many unknowns and variables involved that are unique to each person … if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new (see post #2 here) and you have confirmed that it meets the minimum quality/durability specs relative to your BMI range that are suggested in the durability guidelines here then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” beyond that would be higher as well.
A 2" quilting layer of lower quality/density polyfoam is only a little thicker than the guidelines suggest and your lower BMI range would also work in your favor (although not for your husband) and the quality and durability of the materials is also better than most of the mainstream mattresses that are available in the industry so it’s “not bad” but it’s also “not good”. If the mattress is also “on the edge” of being too soft for you then the risk would be higher because in this case even a relatively small amount of foam softening can take you outside the comfort/support range that would be suitable for you although rotating the mattress on a regular basis would also be worthwhile (see post #2 here) so he would only be sleeping on one side of the mattress for half the time.
It’s also interesting to note that these specs would be better than almost all of the mattresses made by the top 3 manufacturers (Sealy, Simmons, Serta) which by themselves have a market share of about 56% of the industry and they would also be better than most of the mattresses made by the other top 15 manufacturers as well and the top 15 combined have a market share of over 90% of the industry (see this article).
Overall … it would be reasonable to expect the mattress to maintain its comfort/support for somewhat less than the 7 years that I mentioned and it would take “luck” for it to last longer but how much less would be impossible to predict for certain because of all the many variables involved.
Phoenix