I smoked my first brisket on my PK grill today and....
It seems to be done and quite tender at 7 and a half hours. I smoked it for 5.5 hours then 2 hours in a crutch. It uniformly measures 195 throughout and the piece I cut off the flat end was quite tender. Is this even possible for a 10 lb untrimmed brisket? I know brisket is variable, but wow....
Oh, details - my grill was measuring 225 up to a high of 300 after some additional coals. No mopping, just adding wood every half hour or hour. In the oven with the crutch at 250.
Also, is there any particular advantage of resting it in the cooler instead of a 170 oven?
Personally, I've never done the foil/cooler thing. When I've done the Texas crutch, I'll put the meat back on the pit to dry out the crust or open the foil up so the bark can crust up again in the oven. If you got the flat and point to the same temp (195 or so) there's not much you can do to it.
Had an old pitmaster tell me 30 some odd years ago that a brisket is done when it's done. Time is kinda a guideline but nothing written in stone.
Re: crutch and cooler:
I used to be a purist, too, when it came to the subject of brisket, if only because I'm an immense fan of a good, crusty bark. And fair enough, if there are no time pressures, I'll still do a non-crutch, non-coolered hunk of meat. Smoked at 225F to 203F internal, it's a beautiful piece of meat.
Where the crutch and cooler come in handy is when you're having a meal for a crowd at a certain time, with other jobs for your Q (I smoke on a BGE, which means it's also my grill) before you eat. Frankly, when there are timelines involved, I find that it's invaluable to be able to hurry up the cooking process, finish it 2-3 hours before serving, and then bring it out piping hot. The same technique also means that you can make your meat at home and then transport it reliably to other places or backyards.
Rather than saying "it's done when it's done", the crutch/cooler allows you to aim more generally for a window of time, that allows for a lot of give both on the cook and on the hold- absolutely invaluable when cooking for a hungry crowd who want to know when supper's to be served.
The last one I did was a 13.5 lb whole packer, and to my amazement it was done in 8 hours. On the smoker at 225 for 7 hours, followed by just 3 hours in foil in the oven at 225.
At the 8 hour mark I decided, "Gee, I better start checking the internal temp" assuming I still had hours to go, and actually it was at 203 and really perfect for slicing. Glad I checked it then.