On my last pork butt, with 8.5 pounds of meat, I started at 4:30 a.m. in the morning. At 3:00 p.m. the next afternoon I gave up trying to wait out the stall and foiled. I took it out of the smoker at an IT of 205 degrees. It was about 6:00 p.m.
The size of your meat and the smoker temp make a huge difference in cooking times. A three pound roast will often not stall at all when smoking at 225 degrees, whereas an eight pound piece of meat can take 4-8 hours to get through the stall, leading to cooking times that go way beyond twelve hours, as mine did.