The best way to find out if it's time for a new mattress is to ask your body. Do you wake up with aches and pains? Do you toss and turn a lot throughout the night? Can you see excessive body indentations and deep cavities in the mattress? These are the best ways to determine whether or not your mattress is still capable of properly supporting your body. If your mattress isn't delivering the amount of comfort and support your body requires for healthy sleep, then you should purchase a new one.