I've done overnight and right before they go on, and I really couldn't tell enough of a difference to make it worthwhile. I rub right before I throw them in the smoker now. I would definitely recommend trying some different rubs and see how you like them. Oak Ridge is great, I use Blues Hog on all my ribs now. Just find what you like, the test runs are a great excuse to cook!
BWS G2 Party; 2 Maverick ET-732's; Weber Genesis E-310