Your mattress has memory foam on top and firm poly foam under it. The memory foam is where you problem lies. If you flip it over and add 2" of soft latex foam to that, you'll have all the surface comfort you'll want, and it will last a very long time.

Also, if you have a queen or king size, double check to make sure your bed frame has a center cross bar with at least 1 leg attached that extends to the floor. On occasion, lack of center support is the culprit behind sagging/softening. You will also want to check your boxspring for any bending/sagging at the center as well. Just a tip. Good luck. NN

We have a Simmons Comforpedic Luxury Plush. After a few years (at least three, maybe five?) it has persistent body intentations. My wife and I tend to sleep in the same basic locations and once that gets started, the indentations keep you there and it just gets worse. One persons "memory" and "contouring" is another persons lack of support and indentations. We used the frame and box springs that came with the mattress. The floor is padded carpet on a concrete slab, so the mattress could not be more solidly supported.

Definitely rotate the mattress 180 degrees. For me this improves my lower back posture but my hips end up in about the same place. But it's free and it helps.

I'm considering flipping it over and adding a comfort topper. (What do I have to lose?).

Note that sagging overall is not my experience. If your foundation for the mattress is not dead flat and evenly supportive, you don't have a mattress problem - you have a foundation problem.