How often should you change your mattress? The tell-tale signs it's time for a replacement

Bedroom with wood panelled headboard and red and pink bedspread.

Wondering how often you should change a mattress? We're here to help with a round-up of the sure-fire signs your trusty mattress is past its best and in need of replacement. 

Of course, if you've invested in the best mattress your budget allows, then most of us want to hang on to that mattress as long as possible. Especially considering that even if you take advantage of some of the best mattress deals going, mattresses don't come cheap.