Thanks for the tip, Siege!
As for prepping butts, I trim and rub mine the night before and wrap with cling film. The next day I apply more rub before putting it on the grill. I have done it all the same day, and I admit where wasn't a huge difference in taste. But, I like getting the meat prep and smoker prep out of the way, so on cooking day I don't have so much to do. Beside, a longer marinade has to be better (at least in one's mind).