I smoking my first Boston Butt that weighs in at 10.2 pounds. The rule of thumb for smoke time is 1.5 to 2 hours per pound. In everyones experience should I plan on it being closer to 1.5 or 2?
If you plan on 2 hours, and it finishes early, then double wrap in heavy foil, then a large think towel, then pop it in a cooler to hold till ready for serving. The butt will stay remarkable hot for quite awhile. Same holds true for brisket.
I left a probe in my last pork butt (9.5 lb) while it rested. Double-wrapped in foil, then a towel, then in a not-fancy Igloo Playmate cooler. It took 6.5 hours before it got down to 140. You've actually got a few hours after that before you need to even start worrying about any food safety issues. So I'd go with 2 hours/pound. It only gets better as it rests. And you want to avoid pulling it from the smoker early because everyone is waiting and hungry.
The end of smoke to done, then double wrap and rest is critical for a finished BB.
I find; 6oz @ 225 + time to 195, no peak, wrap and about 4 hours rest to be "ballpark" on most. But But...each smoke does vary by degrees of "sameness" which is the unknown in the final and unique "finish".