Can I rest a butt for 3+ hours

Shouldn't be an issue , I have a smaller cooler and insulated with towels and I can rest butts or brisket for 4+ hours. I generally don't do more because I want to eat my food sooner 😁

Yes if it’s still 200 dg going into the cooler it should be good for several hours. Doubt it will even need reheated.

Yes. This is incredibly common and most people do that even cooking at home.

I've finished meats the night before, wrapped in foil, several towels, and put in cooler. They are then still steaming hot the next day for early dinner when I pull them out. They are always incredibly moist, and everyone is amazed at how tender.

Super long rests are ideal if you can swing it.

Absolutely.

I once cooked 2 pork butts and then stuffed them in a cooler and took a 4 hour ride. When we pulled them out they were still steaming hot and delicious

Long rests are indeed the way. 4 hours minimum. Always come out great.

Perfect. I appreciate everyone's feedback.

I believe 6 hours is about where you start pushing it...

I leave my temp prob in my butts when I put them in the cooler and it is usually takes about 5-6 hours before it gets around 150. I like to start the night before finish in the morning and let it rest for at least 4 hours before pulling.