10 years ago I bought a Sterns & Foster, which started to sag directly on the low pyle carpet. It started off as rock-hard and eventually I woke up in tears from back pain as I was now like a pretzel.
I bought a fancy Luma Sleep(RIP them) latex hybrid as those were supposed to last a long time. It started out very firm(which I like) and with the topper it was good for ~2 years. Then came the sag, as soon as I get on the mattress I sink. I removed the topped which helped a bit, but now I’m more comfortable sleeping on the tile floors then the mattress. Should only after 5 years I be having these issues? I’m 5’10 180lbs and a back sleeper, my partner is 4’10 and also a back sleeper and is also suffering.
Latex, varying foam density, hybrid, coil, quantum nanite buffering supports - are these actually good designs that I’m somehow missing or having bad luck with? I see mattress lifespans from 7-20 years, but I’m lucky to get 25% of that before they are causing problems 
Now that my vent has concluded, I’m just wanting something that’s good for my partner and I that are hot back sleepers and like the firmest things out there and don’t feel like an overused stress ball after sleeping on them overnight, let alone repeated nights…