Huh. Close to a simul-post Kao, i didn't see your response earlier.
I've been running the cords differently. Some of the headsets run from the PC (under desk) right out to the front of the desk. The latest one (the newest) I had run up the access hole in the back of the desk, but that caused a bit more tension since there was less slack. I don't hang them by the wire, I just gather up the wire and dump the headphones onto the desk. There was an old set that got chewed on a bit by cat and/or babby, but that didn't start dying until after about two years. The others have no noticeable damage and lost channel after only a few weeks.I don't plug/unplug them at all until they start to die and I start trouble-shooting.
Now, onto something else I've noticed: my son has his own laptop in the living room and he uses cheap headphones to listen on. Those also have been losing the right channel after a few months, but that I had been attributing to abuse by children (his four year old cousins will fight over the laptop and headphones). So apparently I've passed on a gene to my son that kills the right channel of headphones.