According to this study, you should throw out your underwear and buy all new every year.  Who does that??  And I feel like this is brought to you buy the people who sell underwear.  But anyway, what's the longest you've ever gone with the same pair of underwear?  Most people... I hope... change it daily.  I know people who change them twice in single day.  Then, there are these people...

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It gets worse... and who's THE worst??  Check this out...

They also say that you should also change out your underwear once a year because of possible E.coli.  Gross.