Hi schmiggyjk,
Yes … a two sided mattress will extend the life of any foam material … even one as durable as latex. I would want to know the details of the “other layers” though because they would not likely be as durable as latex although having it two sided would extend their lifetime as well.
This is more of a personal preference and budget decision. If I did use polyfoam as a support layer (a latex hybrid) … I would make sure the polyfoam was good quality (at least 1.8 lbs and preferable higher) and if there is also polyfoam in the quilting layers above the latex then i would want to know it wasn’t more than around an inch or so (more than this and the polyfoam can become the weak link of the mattress). All of this would depend on the density of the polyfoam as well as the specific layering because there is a wide range of quality in polyfoam and the design and layering of the mattress will also make a big difference in its durability.
You can see my thoughts about a polyfoam/latex hybrid vs an all latex mattress in post #2 here.
You are in the enviable position (compared to most people who shp for mattresses) that your choices are good ones and it would be difficult to make a “mistake” no matter which direction you choose to go. I know how difficult it can be to make final decisions when all of your choices are good ones (and you don’t really wan to eliminate any of them or you want some parts of all of them) but if you consider the differences in how each mattress feels and performs in terms of PPP (Pressure relief, posture and alignment, and personal preferences) and all the other factors and tradeoffs involved in your personal “value equation” then you will eventually come to the best decision … for you.
Phoenix