I've been trying to read reviews online and I keep seeing "developed sags after just a few months/few years" - I know they don't last forever, but I need more than a few years out of it. This is what happened with our verlo. But I also can't spend too much. I'm afraid that if I lay one one, it'll seem fine for 5 min in the store - but after some time it will be different. And I really just want a basic spring mattress.