Gotta get them to that magic internal temperature where the connective tissues start to break down, then let it sit there for a couple hours. I usually start mine at 11pm and run them until about 4pm the next day. Pull them out, foil-wrap, then place in an empty cooler surrounded by dry bath towels to rest for a couple hours before I serve it. When I pull it out of the foil, it's usually still steaming hot.
I've followed some good advice, is all. I'm not about to go reinventing the wheel.
On a long cook of pork shoulder, the only things that can really go wrong (aside from not cooking it long enough at that "magic temperature," which will result in disastrously tough meat) are: A) your fire goes out while you're snoozing, or B) the fire gets way too hot while you're snoozing. Both situations are recoverable, if you catch them soon enough. If A), it'll just take longer before you can eat the next day. If B), you might have some tough bark to contend with.
and they say that pork butt shoulders are more forgiving than others.
sidenote: try not to panic if the I.T. stalls at around 150 for too long. I've heard that it stayed as long as 6 hours. it's normal.
then when it hits 190, you can break out the bubbly.
i love you 190 degrees!
In case some of you are looking for work:
Took around 8 hours total for a 4lb butt. That was longer than I had expected. I usually figure its around 1 1/2 hours per pound. Temperature usually stalls around the 170 mark, but then begins cooking again. I pulled it out at around 195. Just had some leftovers for lunch. Delicious.