Foiling is a personal preference or a timing thing. If you have the time you could leave it get to temp in the smoker, remove, wrap in a double layer of foil and put it in a cooler. When you put it in a the cooler make sure you take up all the empty space with towels or crunched up paper. I've kept pork butts and briskets, safely, for 5 hours.
If the butt is taking longer than expected, you could wrap in a single layer of foil when it hits 160 - 165 degrees and put it back in the smoker. Check it after about an hour - hour and fifteen minutes for desired temp. When it hits the desired temp double wrap it and continue as above.
In either case try to let the butt rest for at least an hour, two is better. When I've smoked them at home, there have been times I've wrapped them in layers of towels and left them on the kitchen table for and hour or so. I've been told that somebody (on the comp circuit) uses a sleeping bag to hold his meat.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ed Cardoza:
I am going to be smoking a pork butt for Xmas and was wondering if I should foil it and put it back on the smoker after it reaches a certain internal temperature, or should I just leave it alone and foil it when I am done then let it rest for a couple of hours.
smokingandlovingit...
TVWB Rookie </div></BLOCKQUOTE>