You can probably cook a hot and fast butt in that time (or maybe starting a little earlier) but you may not hit your timing the way you want.

Yesterday I cooked four 5.5 lb pork butt roasts (that's all our local supermarket had) and started them at 7am. I ran my smoker around 260 for most of the day (I bumped it to 270 for a little while). Around 2pm I put each in a foil pan with a little apple juice and covered it with foil and popped back in the smoker. The resulting steam helped them finish by 3pm. I pulled them out of the smoker, removed them from the foil pans and wrapped each in foil (saving the braising liquid in a large Pyrex cup). Then I put them in an old cooler and covered with towels and they sat there until it was time to shred them around 6:45. When I shredded the meat I added back some of the heated juices, sprinkled with a little more of my BBQ rub and added some Kosher salt (I don't like bland pulled pork). Worked perfectly.

For 8 lb. butts, they would have needed a few more hours and possibly would have needed to cook hotter. I don't like going over 275 unless I absolutely have to.

I would start late the night before at 225 and then you can see where you are at when you get up tomorrow morning.