I just had my (second cook), first overnight cook of two 6lb pork shoulders in my XL BGE. They turned out great!
I had just made some filet's and then got the egg down to 220 degrees. I used the plate setter, put on the two shoulders at 8pm. I didn't go to bed until 11pm, so I had a chance to check to the temps a few times. I was shocked at how steady the egg kept the temp. I woke up at 5:30am and went out and checked the egg, it had gotten down to 200 degrees. I made a couple of adjustments and got it back to 225/250.
I took them off at the 18 hour mark!
We had them tonight and they were very good. Can't wait to try some other dishes. I do need to check my temp gauge thought, as it seemed awful long to hit 190 degrees internal meat temp.