That seem like a long time to keep the temp in the safe zone. Once your meat goes under certain temps the bacteria can grow very rapidly. You want to keep it above 140 IIRC. How big is the butt it could stay hot enough or you could just reheat it. Are you sure it will be done that early? You could turn the heat down and possibly stretch out the cooking time if needed. I start butts at midnight generally and sleep all nite but I'm comfortable doing so with my cooker and maverick therm.
Question...The surface of the Butt is 225°+, all Bacteria are long dead. It is double wrapped tightly in Foil, no leaks, and Towels. It is in a Clean Cooler that has not been opened while the OP Sleeps. Let's say some 6-8 hours later the temp of the meat has dropped to below 140°F...What Bacteria is going to start growing rapidly?
Now being more serious...Yes, there is a remote possibility that some Spores have survived all that heat during a long cook Butt, they also need low Salt/Sugar Moisture as both bind up available water and Smoke is Antiseptic. Additionally, any newbie bacteria need temps in the 90 to 100° range to grow quickly.The Butt would have to be in that Cooler maybe 15 hours for this to happen, including no Rub or Smoke on the meat.
There is really nothing to worry about even if the OP over sleeps and the Butt does drop below 140°F. I'm not trying to be a Wise-Guy, just pointing out the facts. The recommendation of staying above 140° is to keep folks from leaving cooked food on the Counter, exposed, for many hours...JJ