Hi BobinCA,
You can see my comments about the Aviya mattress in post #25 here along with the comments in my earlier reply to you in your other topic in post #6 here.
The Natural Escape uses 3" of 100% natural Dunlop latex in the comfort layer which is a much more durable material than 1.8 lb polyufoam so there are no lower quality materials or weak links that would be a reason for any concern or cautions in your weight range relative to the durability and useful life of the mattress. It also includes a wool quilted cover which would be a benefit in terms of temperature regulation as well.
Phoenix