Apple smoked a 20 lb turkey at 250ºF in my MAK 2 Star 4 years ago and upon checking my notes I found that it
took me 8 hours for the thickest part of the breast to reach an IT of 170ºF. There are ways of speeding up the process - for example: smoke the bird for say 3 hours with apple, hickory, etc ... and then bump the pit temperature to something like 325ºF until the IT reaches your preferred temp. Word of advice: The turkey will go through a stall during the cook.
Rested the bird for 30 minutes loosely under a foil tent before carving. Used a 16"x12"x3" Aluminum Non-Stick Roaster with “V” Rack for easy handling and capturing the drippings. Stuffed the cavity with Washington State Red Delicious Apples which were tossed after cooking. Only stuffed the apples loosely in an attempt to add some apple flavor. Didn't do much good but be sure not to eat them if anyone were to repeat my experiment.