My Bro-in-Law did a 13 lb packer brisket on his Master Forge vertical propane unit this past Sunday. He wrapped it after 4 hours, and at 7 hours we pulled it and the IT was 209. The door thermo on the smoker was between 200-220 the whole time. I know those are notoriously inaccurate, and I have serious doubts about a 13 lb brisket getting to that temp in only 7 hours cooking in that temp range, but the brisket was fall-apart tender and delicious. Just out of this world. My guess is he was actually cooking around 300F and the double foil wrap helped speed it along. But nonetheless, it IS quite possible to get delicious and tender brisket, even a whole packer, in a 7 hour time frame.