Does anyone out there have experience with a bed/mattress (Cal King)  that is comfortable when new AND after several years of use AND has retained its new-like shape without acquiring wear patterns, indentations on each side of the bed (where each partner sleeps), or a large sink-hole / hammock effect in the middle of the bed ?  Other than a waterbed (or air bed), does such a bed exist?  Or is this an impossibility and an unrealistic expectation?