Hi blackviolet,
Thanks for the update.
All of the mattresses you are considering use high quality materials and there are no lower quality materials or weak links in any of them that would be a cause for concern relative to your weight ranges in terms of the durability and useful life of the mattress.
There is also 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 that are suggested in the 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” would be higher as well.
There is also more detailed information about the variables that can affect the durability and useful life of a mattress (and the materials inside it) in post #4 here and the posts it links to as well.
All of the mattresses you mentioned would be similar in terms of durability but the ones that don’t contain any 4 lb memory foam may be slightly more durable and the possibility of “bonus time” would be higher.
Mattress warranties only cover manufacturing defects and they don’t cover the gradual (or more rapid in the case of lower quality comfort layers) loss of comfort and support that comes from foam softening that is the main reason that most people will need to replace their mattress. In other words the length of mattress warranties have little to nothing to do with the durability or useful life of a mattress or how long it will be until you need to buy a new mattress. If there is an actual defect in the materials it will usually show up early in the life of the mattress (usually in the first year or two) but knowing the quality/density and durability of the materials in your mattress is always a much more reliable way to assess the relative durability and useful life of a mattress than the length of a warranty. There is more about mattress warranties in post #174 here.
They have a 50 day trial period that allows you to exchange the mattress for a different one at no cost but I believe you need to sleep on it for a minimum time (possibly 30 days?) before any exchange but you would need to confirm this with them. They don’t allow any returns or refunds.
The thickness of a mattress or the number of layers or the thickness of any individual layers inside it is really just a side effect of the design and the design goals of a mattress and is also only one of many variables that can affect the feel and performance of a mattress relative to any particular person and by itself isn’t particularly meaningful (see post #2 here). In some cases higher weight ranges (or a higher BMI) will sometimes do better with a mattress that is thicker than lower weight ranges or a lower BMI (see post #14 here for more about the effect of thickness) but even this depends more on the specific design and combination of materials in the mattress and on how well your testing or personal experience indicates the mattress “as a whole” matches your specific needs and preferences in terms of comfort, firmness, and PPP than it does on just the thickness itself.
In other words … the thickness of a mattress really has nothing to do with the quality, value, durability or comfort of a mattress so I’m not sure why this would be important other than if having a sleeping surface that is a little bit higher is important to you.
You are certainly looking at some good quality/value choices and I’m looking forward to finding out what you end up deciding.
Phoenix