Great news! I am back in black with American Airlines: 21,000 miles.
I called them some time ago (when I received the dire expiration message), and received some ideas. The agent told me that if I had used one of their partners (and everyone is a partner) since the last flight, that would count. I just had to call the partner and attach my AA number to the transaction.
I used a rental car last September in Detroit, and bingo, 6 weeks later, I am ready to roll.