The brisket will be fine over night. I do this all the time with my seasoned meats for the smoker. On a low and slow cook I believe the time is normally 1-1/2 to 2 hrs a lb. However last weekend I made a small 5lb flat that went 12 hrs on my wsm at 220*! I did not foil mine until the last couple hours because I did not think it would ever be done! I did foil with some beef broth and to my surprise it turned out great. I really though that I had killed this one and it would be dried out. Brisket for me has been one of the hardest things to make well! Good luck BM!
18"WSM/SMOKEY JOE/ VERY OLD 22.5" Weber /5 BURNER KENMORE GAS