As a side note on this, I’m a huge fan of pure latex mattresses. Just a solid slab of latex. Maybe a few slabs of different densities if you want to get fancy. I’m 4 years in on mine and it still holds up really well, no sag issues etc. if you’re in Canada there is MFC (memory comfort Canada) this is the cheapest place I could find, but there might be a better deal if you dig deep enough.

Agree with this. I’m done with anything with springs.

Before bed in a box was a thing I built my own. 4” of high density foam base, 3” of med density latex, 2” of low density latex on top. I swapped out the top layer a few years back, but the core is still going strong ~14 years in, and it’s still my favorite bed I’ve slept on.

One tip is you’ll want some kind of cover for your latex, since long term exposure to air will cause it to degrade.