I always start my butt smokes around 12:00am-1:00am and it works out really well. I think if you start smoking around midnight and pull at 195 you'll be good.
If for some reason they get done early, you can drop the smoker temp down to 140 when the meat internal temperature hits 190-193 and let it rest in the smoker until 4:00. Since the smoker is insulated so well, it will retail its internal temperature for quite a while (even in the cold Midwest temps), and the carry over will take it pretty close to 195. At 4:00, double-wrap in foil, and let rest in the smoker for 1-2 hours with some towels on top. Then pull at 5:30-6:00 to pull the meat.
Or you can pull the butts from the smoker at 195, double-foil wrap, and let rest in the cooler for up to four hours and then pull.