Hi Eaglenine,
As you probably know from your reading here … you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components would be the best “match” for you in terms of PPP based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing or personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
There is also more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of PPP in post #2 here that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for once you actually sleep on your mattress.
If your mattress is well inside the comfort support range that is suitable for you and not “on the edge” of being too soft (see post #2 here) and meets the quality/durability guidelines here then it would be reasonable to expect that it will last for 7 - 10 years and if the materials are better than just the minimum in the guidelines it would likely be closer to 10 or in some cases even longer. I would also keep in mind that if you are using a mattress for extended periods of time in a sitting position on a regular basis where your weight on the mattress is more concentrated in the middle then this will reduce the durability and useful life of any mattress to some extent as well.
There is more about the differences between an innerspring/latex hybrid and an all latex mattress in post #28 here. I would treat the choice between them as a preference choice rather than a better/worse choice. A pocket coil/latex hybrid and an all latex mattress will both work well on an adjustable bed as long as long as they aren’t too thick to conform easily. This would generally mean choosing a mattress in the range of about 12" or less although there isn’t a “fixed” thickness that going over would suddenly make a mattress unsuitable because it would also depend on the specifics of the mattress so I would make sure you let your retailer or manufacturer know how you are planning to use it so that they can let you know whether the mattress would be a suitable choice for an adjustable bed.
In addition to any latex/innerspring hybrids that may be available to you locally, there are some links to some innerspring/latex mattresses in post #2 here that may be useful as well if you decide to go in this direction.
There is also more information about choosing an adjustable bed in post #3 here and the main adjustable bed topic that it links to that can help you choose an adjustable bed based on price vs features comparisons and also includes some retailers that you can use as good sources of information about the features of the adjustable beds they carry and as pricing references as well (in post #6 in the main adjustable bed topic). I would keep in mind that online advertised prices are often controlled so make sure you call them rather than just looking at websites.
Phoenix