The watched pot...it always seems worse when you are tired or trying to coordinate a set meal time.
I had a similar cook yesterday with an 8 lb and 6 lb butt. I got a late start and wanted to go to bed, but the temps just didn't cooperate. Finally, after 10 hours at 275-300 I got where I needed to be. The funny thing, the 6 lb was at the same temp as the 8lb when I finally pulled them both to rest.
(Insert new smoker here!), Weber WSM-22, Weber 26.75 OTG, Blue Weber Performer with gas assist, Pit Barrel Cooker, UDS with rotisserie, SJG mini-WSM, Weber Go Anywhere