Hi androiddd,
Thanks for the post, … this is the best place for your post as it is easy to follow your previous history and experience with rebuilding your beds.
Good point about rotating these the foams especially for couples that have a larger weight differential (See post #2 here ~ which also has more information about this)
Your first question is one of the most common questions on the forum (ie. which material type or firmness level would be better for me?) Sometimes getting the right mattress/topper combo could be as difficult as getting a new mattress. As you probably know from your previous readings …while it’s not really possible to make specific suggestions because of all the many variables involved that are unique to each person and your own experience is the only way to know for certain whether any mattress/topper combination will be a good “match” for you in terms of PPP, replacing the memory foam with soft latex which is still supportive could take care of your issue. While being supportive because of the push back it would also give the extra cushioning needed and provide the air flow for a more temperature neutral environment.
There is more information about choosing a topper in post #2 here and the topper guidelines it links to which along with a conversation with a reliable and knowledgeable supplier (that can provide you with good information about how their toppers compare to each other or to other toppers they are familiar with that are available on the market) can help you use your sleeping experience as a reference point and guideline to help you choose the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success.
Regarding the “gel memory foam” typically this type of gel foam conducts heat from the body (like putting your hand on a marble countertop) and is “thermally conductive”. It transports heat directly away from the body and releases it into the surrounding atmosphere (as long as it is cooler than the gel) without needing something to “carry” the heat away.
FYI, this type of gel memory foam will cool at first for a while until the temperatures equalize and then the foam would once again become an insulator and trap heat. It may provide an extra cooling effect when you are first going to sleep and the foam will feel cooler to the touch but neither of the gel technologies provides as long-lasting cooling benefits as moisture wicking, storage, and ventilation. The higher the percentage of gel the more effective and longer lasting the effects of the gel will be.
Aside from the “not rotating” the comfort layer, your memory foam toppers only lasted 2 to 3 years. This is one of the issues with recommendations from Amazon or FBM and one of the reasons why we wholeheartedly recommend our trusted members who meet a set of rigorous criteria for their products, and services before we include them on our site. Many times when buying from unknown sources, you’re never really given all the specs that would allow for an informed decision. In this case, you don’t know the ILD (firmness), only the density. Many of our members use a soft/firm choice for each side of the bed, but most of the time this is done with latex foam, primarily with Talalay latex, as Talalay has more firmness ranges than memory foam and other latex foams. If you like the feel of latex, of course, you have many options that are much more durable and have better temperature regulating qualities than gel or any of "temperature enhanced "memory foams.
While at first glance this may not be quite the answer you’re looking for I’d first make sure that you do not end up with a top foam layer that will break down rather quickly as you can easily find yourself in the same place 2 to 3 years later.
Once you have a chance to read through the links I provided let us know if that generates any new approach to your bed rebuilt and questions.
Phoenix