Hi Glenn,
While all foam including latex will soften over time … latex will soften considerably less than polyfoam or memory foam which is one of the reasons it is so durable. When there is a thick layer of wool or other natural fibers over the latex … it tends to compress over time which makes it firmer and reduces the ability of the latex underneath to take on your body shape and relieve pressure. While certain types of construction can reduce this (such as tufting), the tendency is still there. Many manufacturers are using thick circular knits without quilting over latex (especially softere latex) for this reason but without wool … other methods of fire retardency need to be included in the mattress (Natura uses wool in combination with Borax for fire retardancy).
There is more information about the effect of wool and quilting in post #87 here
In terms of the Natura’s value … it is good compared to normal Natura pricing but Natura pricing as a whole is quite high (although it is a quality mattress) and 20% off still doesn’t put it in the same value range as most independent manufacturers either local or online IMO.
Having said that … there is always something to be said for buying a mattress which you have tested for pressure relief and alignment even if the price is higher. “All sales are final” though means that there would be no chance to adjust your mattress if your longer term sleeping experience was different from your testing while with an online DIY purchase you retain the ability to make adjustments if necessary and the “value” in terms of materials and price would be significantly better.
As I mentioned in the post about quilting though … everything involves tradeoffs and the components that make up “value” are different for different people depending on what is most important for each person.
Phoenix