All we're doing is eating at a local restaurant that gives f.f. miles and that counts as activity!

This is from their website:
Mileage Expiration Policy
Miles earned in the Dividend Miles program do not expire as long as the member has any type of qualifying account activity within the past 36-month period.

Mileage Expiration Policy Update: If you have not had any account activity (miles deposited or debited) in the past 36 months, your Dividend Miles will expire in the first quarter of 2006. Miles earned in the Dividend Miles program do not expire as long as the member has any type of qualifying account activity during a 36-month period. If you haven’t had any activity in that time period, your miles will be subject to expiration. So, start earning miles again on US Airways or use any of our partners worldwide to retain your miles. You can even earn miles by purchasing flowers, staying in hotels, renting cars or in many other ways with our Dividend Miles Partners