Hi will.i.am,
You’ve found the posts I usually use as a reference for questions about two sided mattresses (post #3 here and the posts it links to).
In most cases a two sided mattress has the core in the middle and then has the same comfort layers on each side. With this type of construction you could use both sides because they are the same. You will sometimes find two sided mattresses that are finished and suitable for sleeping on both sides where each side is different but you would lose most of the benefits of having a two sided mattress with this type of mattress because most people would only use the side that they prefer and the other side may not be a good “match” for them in terms of PPP.
If you mean can you use a latex layer in either direction or flip it from top to bottom then yes. Talalay latex is more consistent from area to area and from top to bottom in terms of its firmness while Dunlop latex that is poured in a mold will usually be a little firmer on the bottom than on the top but it can still be used with either side up. There is more about ILD variances between materials in post #6 here.
The latex cores themselves are either poured in a mold or on a belt and then individual layers are cut to the thickness that the manufacturer wants to use in a particular mattress design. The mattress itself is a series of layers or components that are placed on top of each other with a cover around it. Different layer thicknesses, firmness levels, types of materials and components, the order of the layers, and different types of cover are all ways that each mattress can be customized to be suitable for different people. If the mattress is two sided then it can be used either side up. If it’s one sided then you can’t flip it but in most cases they can be rotated (as long as they are symmetrical from the head to the foot which is the case with most mattresses) so that you can sleep on different parts of the surface which can lengthen it’s useful life.
All foam materials get firmer as you compress them more deeply but they will get firmer at different rates (this is called compression modulus). The progressive firmness you are probably referring to is a common form of layering or mattress design where the firmest layers or components are used on the bottom of a mattress and then the mattress uses progressively softer layers as you go up to the top. This allows for softer comfort layers on the sleeping surface for better comfort/pressure relief and firmer layers deeper in the mattress for better support/alignment.
It can be yes but I think the posts you linked cover the pros and cons of one sided vs two sided so each person can decide whether it’s something that they would prefer. There is no “right or wrong” answer here. For most people it would probably depend on how well the mattress matches their specific needs and preferences in terms of PPP, whether they are comfortable with flipping the mattress every couple of weeks at first and then every 3 months or so after that, on whether the additional lifespan of the mattress was worth the additional cost of a two sided mattress vs one sided, on the type of mattress, and on the other mattress options they had available to them. With latex it may not be as important to some people because latex is already a very long lasting material but even with latex a two sided mattress will extend the life of the mattress.
Phoenix