how often do your earphones last?
i changed a few times the last 12 months. its always the left earphone that lost sound.
i am unable to pinpoint the cause.
i always put my itouch in my waist pouch when i go out or for jogging.
You can consider investing in Shure ones, their earpieces are replaceable, so you either replace the cables or the earpieces.
But they are a b*tch to put on, and taking it off is not as easy as yanking, otherwise your ears will come off as well.
Put them on properly and their sound isolation is awesome. So good you can't hear yourself scream. I swear.