Forfeited Air Miles

I got an email from US Airways telling me unless I fly one segment by September with them or sign up and get a US Airways credit I am going to forfeit almost 19K air miles.
Super bummer. It may actually be worth it to fly one way from Dulles to Norfolk one weekend while I'm in country as 19K probably won't earn a free ticket but possibly a upgrade.

I'm also getting close to losing my miles on Delta, although not as much