Here's something I'm going to try. Let the cards come back so you can mark it in your database, then send a different card back to the address marked current resident with a message that identifies you as the guy that cleaned the carpets in the house. Maybe a welcome to your new home type thing.
I had alot of folks move between my last mailings, but so far have picked up at least 15 new customers this year. Folks come and go I guess.
Also Greg, I think you can put address correction requested on your cards and they will send it back with the new address.