macbook power adapter problems

[shanti]

i've had my macbook for over a year now. problem is, i've had to change out the adapter once and after 2-3 months, it's happening again! it won't charge my macbook. the light won't go on (green OR orange) on the magnetic lock. when it happened the first time, it sputtered a few times and then just stopped charging.

right now i'm working off my battery, but will be going to the genius bar tomorrow. they replaced the adapter outright at no charge the first time, but i'm worried that this is a recurring event and they'll start making me pay at nearly $80 a pop for a new adaptor. i'm a power user, but don't know if that matters....

anyone else had problems like this and if so, how were they resolved?