Done temp is feel more than anything -- the bone should be "pretty loose".
Will probably take at least 8 hours.
"A full sized pork butt will need to smoke for 6 to 8 hours at 220 to 250 degrees. The temp will rise to about 160 - 170 degrees and then hold there for 2 or 3 hours while the collagen and fat break down and render off."
"As stone said, keep that puppy in the smoker until it hits at least 190. Prior to that fat and collagen are still rendering out. Regardless of time and temp, an easy way to gauge doneness is to stick a standard issue dinner fork in it and give a twirl. If it turns easily the hunk 'o pig be done. Yank it, wrap in butcher paper, parchment or foil (No foil if it was basted with an acidic sauce), and let rest for 30 to 45 minutes."