How long does a helmet last?

[pll]

I found the following article:
http://www.bicycling.com/beginners/b...sh-your-bonnet

This recommendation makes me wonder:

Never dry your helmet in the clothes dryer with your skivvies or in the microwave with your lunch-it'll severely weaken the shell and bonding materials.

*Who* would think of putting a helmet in the clothes drier, to spin and get knocked around!? And *who* would put one in the microwave!?

I don't even use any soap on it... a moist towel is enough to clean any dirt.