I smoke the butts for about 12-16 hours.....depends on what time of the day or evening I start cooking. Once it cooks that long, I put the butt in a throw away aluminum pan and put about an inch of apple juice in the pan. Then cover with foil and cook a few more hours

Anytime I heat up the pulled pork that has been sitting in the fridge, I use a little bit of apple juice as well to help keep it moist when I heat it up back in the oven