Hi mhornbein,
Welcome to our Mattress Forum! 
Thanks for providing your stats and a brief history with your current mattress. Sorry to hear that your “existing Room and Board foam/coil hybrid is significantly no longer comfortable after only 5 years”. At your and your husband’s BMI’s a good quality mattress with durable components should last past 10 years. On the positive side, it looks like you did your due diligence and it is great to see your resolve to ensure both longevity and comfort for your next matters.
You are correct that your husband would benefit from a firmer sleeping surface as a primarily back sleeper and that you as a side sleeper would do better with something of a softer construction (medium firmness may be quite appropriate) to mitigate the several pressure point pains that you are experiencing in several areas of your body.
Latex is certainly a very durable material but there are various factors involved in the durability or useful life of a mattress outside of just the material itself (see post #4 here ) The “weakest link” in a mattress in terms of durability is normally in the upper layers (the top 3" - 6" of the mattress) that are compressed more deeply when you sleep on it and not generally in the deeper support layers so the firmer bottom layers of a mattress will have more effect on feel and performance than they will on durability for most people.
Some of the other factors involved in durability are
~ Softness/Firmness:(Softer is less durable)
~ Position of the foam layer within the mattress)
~ Layers above of below a particular foam
~ One-sided vs two-sided or rotating layers
~ Thickness
~ Person using the mattress (Higher BMI ranges and more active people will wear out the mattress sooner)
Some latex mattresses can last for decades but it will depend on the specifics of the mattress … as a group, they will certainly be more durable than any other foam materials. For those who prefer latex over other materials (or some type of latex hybrid), there is really nothing else that will do. If you are considering a hybrid innerspring mattress it is good to know that an innerspring isn’t normally the weak link in a mattress in terms of durability. Always find out the type and quality/durability of the materials inside a mattress according to the mattress durability guidelines here. You may also want to have a look at post #3 here. and post #12 here. and post #404 here.).
Latex Dunlop vs Talalay durability is an ongoing discussion in various places on the internet for many years … The actual durability of any latex will depend a great deal more on how it is used and how it is protected as it will break down with exposure to ozone and ultraviolet and certain solvents and some other substances. To complicate things even more it also depends of the type of Dunlop or Talalay used (Natural/NR, SBR/Synthetic, Blended)
Blended Talalay, NR Talalay, and NR Dunlop are likely to be about equal in the higher ILDs (Firmer comfort levels). In practical terms, this means that used in a mattress core they are likely to be close to equal.
As the densities ILDs (Softer comfort levels). go down … 100% NR Talalay may start to fall behind the other two … assuming the materials being compared are of the same ILD. In practical terms this means that in a comfort layer the lower the ILD the durability advantage may go to the NR Dunlop and blended Talalay … even though Dunlop is not usually seen in ILD’s that are as soft as Talalay so an “apples to apples” comparison cannot really be made for the lowest ILD NR Talalay.
There are also some types of Dunlop being made now that use a continuous pour process from either Latexco or Mountaintop in various blends (including synthetic Dunlop from Mountaintop) that are comparable to Talalay in terms of ILD and consistency and are also proving to be very durable materials.
IMO … neither can accurately be called better than another as it entirely depends on the use they are being put to. In certain applications … Dunlop is clearly superior when a higher compression modulus is desirable. In other applications … Talalay is superior when softer more consistent foam is desired. Some of the newer continuous pour Dunlop materials are somewhat in between the two in that they are available in softer ILD’s and can be more consistent in terms of ILD variances across the surface and from top to bottom than molded Dunlop (see post #6 here ).
Since all latex is more durable than most other materials and other types of foam … I would make choices based on which had the more desirable qualities in the application it was being used for, on budget considerations, or on individual criteria and preferences rather than a “better worse” comparison.
In your case zoning systems such as the Vzone offered by FloBeds could be very useful and well worth considering. Zoning, in general, is suitable for people that have more difficulty finding a mattress with the right “balance” between comfort/pressure relief (under the shoulders especially) and support/alignment (under the hips/pelvis especially) or who have more challenging circumstances or sensitivities, body types that are more difficult to “match” to a mattress, more complex medical issues, or who have a history of having more difficulty in finding a mattress that works well for them. There is more about zoning in
this article and in
post #11 here and the additional posts it links to but the only way to know whether any specific mattress (zoned or otherwise) will be a good match for you in terms of comfort, firmness, and PPP will be based on careful testing or a detailed conversation with the trusted manufacturer that has your interests at heart.
You may have already considered the option of a split left/right configuration mattress or DIY which could prove useful in getting the right comfort/support match for a couple with different needs and preferences that need to be designed in the same sleeping system. The “side to side split” is an effective approach where each side of a mattress is layered differently to take different needs and preferences into account. In effect, you would have two different mattresses on each side combined into one cover (or in some cases a different topper on each side of the same mattress) and each side would feel and perform differently. You can read more about this in post #2 here
I hope this adds a bit more clarification to the good research you’ve done thus far…let us know if you have additional questions.
Phoenix