I hear you on the memory foam but hear me out. I want something firm but still very comfortable that won't hurt from hardness in the morning. I like some support but not a ton and I hate sinking into a mattress like foam.

My old mattress crapped out about 5 years ago. I bought and returned several mattresses until I settled on the following. I have a fairly cheap firm mattress from a local store. Firm are normally cheaper by the way. I think it was 650 for a king. Then I bought a really nice 3" closed cell foam topper for $200. I expected it to only last a few years, but it's still great. At least another couple years left. But the mattress is still like new because there's zero cushion on it.

Every mattress will wear. But it's primarily the cushion and weak springs that wear. So BFL is not reasonable but you can extend the life in certain circumstances. Since firm mattresses have hard springs and no cushion, they'll last a lot longer. The topper is essentially the only real wear item. Since they come in different materials and thicknesses, you can dial in your preference easily.