I'm flying DL next week (my only flight during the current double miles promo's). It occurred to me that I had not registered my FF numbers for the double mile promos with any other airlines. Knowing that there are times (rare, but they do happen) when I get bumped and rebooked on other airlines, I spent about 2 minutes this morning to register for the promo on all the airlines on which I have an account.

It may be worth your time to do the same!