Hi ydiseattle,
The thickness of a latex comfort layer by itself will have little to nothing to do with whether the mattress has a weak link or make it inherently more or less durable if the type and blend of the latex is the same. The thickness of a particular latex layer along with many other “comfort specs” that are part of the design of a mattress will primarily affect the feel and performance of the mattress.
You can read more about the variables that can affect the durability and useful life of a mattress relative to each person in post #4 here and the posts it links to.
Phoenix