From the BA Executive Club Handbook:
"Do Miles expire?
Your Executive Club Miles will never expire as long as you earn or spend Miles in each 36-month period."
Meaning that if you either add miles to your account (I think transfers from DC as "earning") or spend them (redemption for airline rewards, car rentals, hotel stays, etc.) at least once every 3 years, your miles will never expire.
[This message has been edited by satish_ny (edited 05-03-2002).]