Hi Lew,
Once you have gone through the initial break in period there is very little and very gradual further change in the latex. In the initial 30 - 90 days however … all the components in the mattress will “break in” and this includes the cover which will stretch and loosen and will also have an effect on how far you sink into the mattress as well.
The other layers on top (such as the mattress protector can also affect this).
Sometimes this initial break in period can seem like more than it really is if you are more sensitive to smaller differences in how evenly the layers compress but with the layering you have there is little doubt in my mind that your mattress will stay consistent in its firmness for many years with only very gradual softening (much less than other types of foam). As you mentioned … using your knees or walking on the mattress can speed this up and even out the process more rapidly
It’s also interesting that even some surface softening won’t affect the support in the deeper parts of the layer.
I think the bottom line is that once your initial 30 - 90 days are over you are likely to be fine.
Yes … I think it would help with less risk to alignment in your pelvis area. It would “displace more” under the shoulders while it would “compress more” under the larger surface area of the hips. It is not as lively or as you say “sensual” as a latex layer but it is great in its own right.
The Cozypure Lanoodles topper would do even more of the same (displace under pointier parts of the body). It is more costly and thinner but also more “springy” and resilient (the pieces are larger and more like noodles than flat pieces) like you would expect from a latex layer. You can see a comparison or what is inside them in the video here.
I don’t know how either would do with an “accident” but I would think it wouldn’t take that long for a spill to go through them once the liquid went through the cover. The Seven Comforts would probably hold more liquid inside it for longer though because it has more material inside so “soak it up” but it would also be more difficult to remove the “offending” liquid and washing them would be problematic. I personally use my mattress protector over them (I own both) because they would be difficult to clean or remove “liquid” from inside them.
You can see some of the mattress protector choices and the tradeoffs involved with each type in post #89 here but I personally would use a protector (not necessarily waterproof) rather than either topper for protection.
I changed it to “Lew”. I can make it all small letter as well if you prefer 
Phoenix