PPGI PPGL steel coil batting and foam layers that are used to insulate the sleeper from the steel innerspring coils break down over time.  This creates a significantly less comfortable sleeping surface, and many people experience a sort of princess and the pea feeling when attempting to sleep on a lumpy, bumpy mattress.  Unlike many fluffy duvets, mattresses cannot be put through the washing machine to evenly redistribute the cotton batting comfort layers.  Once these get thin and lumpy, it is certainly time to replace the mattress.

Sagging is another sure sign that a mattress is done for.  A mattress that sags cannot possibly offer good support to the sleeper.  Sagging happens when the inner core support of the mattress gets weak.  In innerspring coil mattresses, sagging indicates that the steel coils are no longer strong enough to support the bed or the sleeper.  A sagging mattress leads to joint and back pain in the user, because it does not hold the body in proper alignment.  This creates strain on the body. 

Sometimes, it is hard to see sagging with the naked eye.  Removing the bedclothes can make it more noticeable.  However, a sure sign that an old mattress is starting to sag is back pain upon getting up.  This problem will get worse, and the worse the sag gets, the worse the physical symptoms of the user will get.  For this reason, it is important to replace a sagging mattress fairly promptly.

Of course, many people don't need to examine the mattress to know when it is time for a replacement.  Once the mattress no longer feels comfortable, it should be replaced.  After all, the mattress is where the mind and body rest and recuperate.  A comfortable foundation is vital for the body to rejuvenate.