I let it rest for a somewhat different reason. After a long cook, I like taking the meat off and letting it rest while I clean up and get ready for dinner. This usually includes getting the sides ready and whatever else needs to be done in the kitchen. With an overnight, it will generally mean taking my shower and putting on some cloths that don't smell like smoke. Also, I like to do my butts so that I have plenty of time to spare. So generally, I shoot to have my butts done and pulled off the smoker at least a couple hours before I intend on eating. I just find everything goes smoother when I do it this way. I'm not sure if it makes the meat moist, but I've had butts resting for a couple hours and still been pretty hot to the touch when it was time to pull.