In middle age, my wife and I finally got a king size. We found a hyper firm innerspring, flippable and 4 way turnable mattress. No pillow, gell or foam of any kind. It’s deep and quite heavy but my wife still rotates it at will (I do it when if I’m not at work). Whenever we start to feel too much compression or sag, we flip and/or rotate and voila, like new!
We got it less then $1K, I think through Amazon. I post the brand later.
https://www.amazon.com/Dream-Sleep-Highlight-Luxury-Mattress/dp/B011JO9IIA
Super springs also great for anything one might do on a bed besides sleeping, like jumping around and stuff.