How long will this mattress last, and what about durability?

Durability scores 7.2 out of 10, good. A mattress wears in its comfort layer and stands on its core: this one pairs CertiPUR-US certified 2.25 lb high-density foam with 1000 pocketed coils on heavy 13.75-gauge tempered steel that resists sag far better than budget springs. It scores good rather than top-tier because the deep 4-inch plush section carries the most foam in the line, so it softens gradually. The steel core outlasts the surface; rotating it head-to-foot helps.