There are several factors to take into consideration when deciding if you need a new mattress. Below are some signs that your mattress has lost its support: 1. You tend to sleep better at other places than at home. Your mattress shows visible signs of wear (saggy or lumpy). Rotating your mattress no longer provides the desired comfort change. Your mattress is 5-8 years old (this depends of the type of mattress and longevity) You wake up tires or achy.