Hi mamaccino,
The Dunlop in the Plushbeds mattresses is GOLS certified organic … and 100% natural but all the latex you are likely to encounter (either Dunlop or Talalay and whether it uses natural or synthetic rubber or a blend of both) will have either an Oeko-Tex certification or an Eco-Institut certification. The cotton in the cover is also organic.
If you are in Portland then the better options and possibilities I’m aware of in the area are listed in post #2 here.
There is more about how I would assess the “value” of a mattress purchase in post #13 here. There are also many factors involved in the final cost of a mattress (see post #14 here). The bottom line though is that a mattress is more than just a commodity where the value can be measured by the cost per inch of foam or the price per yard or pound of fabric or fibers and value always depends on how it compares to all the other mattresses you are considering in terms of suitability (how well you sleep on it), durability (how long you will sleep well on it), and the other parts of your personal value equation that are important to you.
Latex doesn’t “harden” over the course of the night but she may have meant if your mattress is firmer than your ideal and creates pressure points then you will feel this more over the course of the night as the pressure builds up but this is true for any mattress that is too firm for you. Latex can also be deceptive because it has an unusual combination of softness and elasticity combined with good support because it firms up more quickly than other types of foam as you compress it more deeply. Latex is a highly resilient material (resilience is measured by the percentage rebound of a ball that is dropped on the material) which means that it “rebounds” or “pushes back” against pressure just like any other resilient material. Unlike slow response materials which have no resilience at all … it has a more “on the mattress” feel rather than an “in the mattress” feel and is more “motion friendly” rather than “motion restricting” that is more common with low resilience materials. It is less resilient than innersprings and more resilient than most polyfoam. There is more about the properties of latex in this article and in this article.
Phoenix