Wow, that's a really long time for a 10-pounder! I recently did an 11 lb packer @ 225 - smoked it unwrapped for 4 1/2 hours, then foil-wrapped when it hit the stall (the wrap is called the "Texas crutch." Helps retain the moisture and prevents evaporative cooling, which is the cause of the stall). Total time in my #1 to 195 internal was just under 12 hours. Kept it wrapped, resting in the cooler for an hour. Meat came out very tender and moist.
Did you open the door much during the cook? Are you using an extension cord, or plugged into a good outlet? Sounds like something's amiss with this. Bet the family wasn't happy about eating brisket at 2 a.m.!