Hi EricK,
The durability of a mattress depends on a combination of many variables including the specifics of the foam, the firmness and design of the mattress, and the person sleeping on the mattress.
There is more about durability in the quality/durability guidelines here and the posts it links to that discuss durability in more detail but if the quality of the materials in your mattress meets the minimum guidelines then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and if they are better than the minimum (which is likely to be the case with your mattress) it would be closer to the 10 years or even longer. After 10 years the useful life of any mattress would be “bonus time” regardless of the durability of the material but with latex the odds of additional “bonus time” or even “extended bonus time” would be higher than with most grades of polyfoam.
This is a fairly common “feeling” for those that aren’t used to sleeping on latex because it is very “point elastic” (it contours to the shape of the body) so some people “feel like” some parts of their body are sinking in more than they are used to even if their spine is in good alignment.
Phoenix