That depends on the quality – quality and price tend to go hand in hand. A cheap mattress topper might last only 2-3 years, why a high quality topper may last 5 – 10 years depending on how you care for it. Turning it helps, and giving it a wipe down with a damp cloth will help it last longer. Also, the higher the density the longer it should last. A 4lb mattress topper should last longer than a 3 lb mattress topper for example.