There are a bunch of ads floating around trying to scare consumers into buying vacuum cleaners, mattress treatment products, and new mattresses.  The claim is that your mattress will double in weight in 8 or 10 years, presumably due to skin flakes, bedbugs, dust, and other debris.  Well, that not only sounds disgusting, but … yes! Inane!

Here’s a great article I ran across on it:
http://www.straightdope.com/columns/read/2545/does-a-mattress-double-its-weight-due-to-dust-mites-and-their-debris

Be sure to read all the way to the bottom – good advice for scientists there.  But, if you don’t feel like linking over there, the bottom line is: Not true.