The night before a long cook, I do any trimming required, apply rub, wrap in saran wrap, and place it in the fridge. I even prep the smoker as far as getting the ring filled and water pan cleaned. That way, at O dark early the next AM all I have to do is take it out and let it rest while I light the chimney, make a pot of coffee, dump it on the unlit, fill the pan with hot water, turn on the ATC, wait about 30 minutes for thick smoke to clear and pit to come to temp, and place the meat on the rack.
Like Stuart S., It's more about time management than adding flavor for me.