You'll get a one-time score ding for using an account that hasn't had any activity in 3 months (might be 6 months.) As I said, it's one-time, and your scores will be back up the next month, but you do need to know it's coming.
My main concern would be that the account gets closed for inactivity. Not the end of the world if you have high average and overall history, so that it won't affect you in 10 years, but another thing to keep in mind.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007