A 4lb pork shoulder (or Boston butt) at 250F should be about a 8h cook. We've done 6-7lbs and they finished before 10h.
The temperature probe is key. I take mine off at 195F and it usually climbs to no more than 200F while resting.
The equivalent 7lb brisket took about 12h at the same or slightly lower temp (between 225 and 250F).

We are doing ribs either tomorrow or Sunday. I'll nab some photos if the wine bottles don't get in the way.
Going back to the 2-2-1 idea.

"Those who preach the myths of audio are ignorant of truth."