Man o man, that butt turned out perfect! As you can see from the first photo, the natural pop-up thermometer told me that it was ready. I took a few shots before foiling for later this morning. In one, I turned it upside down to show the intact fat cap. I peeled a little back to show the gelatinous fat. I know that some of you remove this, but when it's in this state, I like to let it melt into the pork when I pull it. I broke it into a third and two thirds for foiling and quality control purposes (ya know I gotta!). The pork was really moist and tender. The bark had a nice snap to it. And the smoke ring was very nice.
All in all, I can report that you can indeed smoke an 8 and a half pound butt for 6 hours at a moderately high initial temp, pull it and hold it overnight at 180. As I mentioned in an earlier post, I started the butt at 8:20 yesterday morning. I put it in the oven yesterday afternoon at 3:15 and didn't turn it up to 190 until 4:00 this morning (obviously almost 13 hours!). I then cranked it up to 200 about 6:30. Keep in mind that I have to cook at higher than normal temperatures in the kettle for the first few hours (although the temp does drop after about an hour) so, if you are cooking exclusively at 220, your timings might be different. But really, since 6 hours is about the max for the butt taking smoke, you can pull it and stick it in the oven for hours at 180 without worrying. I didn't take a single internal temp, but I'm pretty sure that internal temps were probably hanging around 180. The nice thing about this is that you don't worry about plateauing, since that's going to happen during the night. If you keep it in for 8 hours, there shouldn't be any danger. Then, all you have to do is raise the temp to 190 for a couple of hours and let the temp come up. Finally, crank it up to 200 for an hour or so. Obviously, you have a big fudge factor, but you probably don't want to leave it in there for much longer than that for fear of it drying out.Total "cooking time" was around 20 hours. At that point, you can foil it and keep it intact for pulling for another 4 hours with the foil/towel/cooler method.
So, here's another technique you can use if you're cooking for 24 hours out but don't want to cook a butt and hold it in the fridge for reheating. This way, you can do the tending the fire thing for 6 hours, drink lots of beer, and then just stick the thing in an aluminum pan with a sheet of foil loosely laid over the top and go to sleep. Pretty cool.