You could hold it in the smoker, many will run a program at 140 and hold food that way, as the 140 is the safe temp. I set that on my 3D as a just in case, but don’t hold it in the smoker when done. I wrap in double foil, a towel and small cooler.
If you need it to cook, turn the temp up. Do you have a digital? I cook at 250-275, and that cuts time fairly well.
But, hope you enjoy the brisket!