Hi derrunner,
There are many variables that contribute to the relative durability and useful life of a mattress including the mattress, the person themselves, and how suitable a “match” a mattress is in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences). There is more about the factors that can affect durability in post #4 here and the posts it links to.
One of the most important parts of assessing durability is identifying any weak links in a mattress (lower quality materials in the upper layers particularly) and I suspect there are more layers than just the latex and innerspring in the mattress you are considering which could be a factor in its durability. If you could list all the layers and components (from the top down) including the thickness, and density of any polyfoam in the mattress I’d be happy to help you identify any potential weak links. A good retailer should be able to provide this for you.
Phoenix