Hi PlushNotFirm,
Latex is very durable and their website says 10 years or more which I don’t think would be unreasonable at all.
Because latex is very resilient and supportive (has a high compression modulus) even in lower ILD’s there is more room for error with latex than with other materials but I would still tend to a little thinner just to be on the safe side because you already have some “soft stuff” on top of your mattress.
The Seven Comforts will be more along the lines of pressure point relief because the microrods will both pack together (they can be fluffed up) and compress. The price on their website is a little more than Amazon but they are still very good value IMO. We like ours a lot
Edit: see post #52 here first if you are considering ordering this topper.
A 19 ILD latex topper will just compress and will be more of a “whole surface” softness and feel softer overall (just to give you a sense of the difference).
I would put the wool mattress pad over everything with the topper (of either type) and the mattress underneath it. You will still need a cover for a latex topper yes to protect it from ozone and ultraviolet and oxidation which will degrade the latex more rapidly. A good cover is important with latex.
Phoenix