Anything that changes the balance in your account, be it earning miles or spending miles, is considered activity and will defer the expiry date by another three years.
It sounds like you have a nearly dormant AA account? There are many, many different things you can do to get some "activity" there. 1) Sign up for AA's e-Summary. You'll earn 1000 miles two weeks after you receive the first one. 2) Join AOLAAdvantage. Just for signing up, you'll get 500 miles.
There are plenty more, but these are by far the easiest ways.
FewMiles..
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FlyerTalkers' Resources on the Web:
http://home.webflyer.com/fewmiles/
Unofficial Guide to AAdvantage:
http://home.webflyer.com/fewmiles/AA/
Unofficial
oneworld Info Desk:
http://home.webflyer.com/fewmiles/oneworld/