Last time I was in the Apple Store I was swapping a MacBook Pro power cord that had worn out through light usage after I’d given them a call. The genius at the Apple Store tried to backhandedly accuse me of abusing AppleCare.
I told him if it does this in less than three years with my MacBook Pro, which hardly ever leaves the desk, then they have a serious quality problem. (Whoever I talked to over the phone clearly knew it.)