How Often Do You Throw Your Underwear Away? [POLL]

It turns out that your underwear may have a shelf life.

It's now being said that you should throw your underwear out after a year, regardless of their condition. Apparently, there are washing machine resistant cooties that stick around. This is pure madness! Why would I throw away a pair of undies that still have a string or two of elastic still in the waistband?