I have not had the guts yet to try the overnight thing yet. I just get up early and go from there. My UDS seems to creep up after about two hours in to the smoke, my guess is because the drum gets to temp?
If I were more comfortable with the smoker holding temp I would start it the night before. You can always rest the brisket but if it aint done....it aint done.
Good Luck and lets seem some pics when it is finished!