My 2 cents: Look at cook times per lb of weight of brisket and butt and time your ons about an hour early. the extra rest in a pre-warmed cooler generally won't ruin your meat half as bad as undercooking a brisket. Under cooked over smoked brisket is nearly impossible to eat, I speak from experience and make sure you check your temps every hour or so. (I had my kamado run away on sunday with a turkey after 2 hours of in-attendence, the squeezin's ignited and flaired the kamado up to 500 from my 370 then I cooked a cottage ham and that too suffered due to the squeezin's in the pit.) Lesson learned: Drip pans help stop flair ups.
Also if you don't have a grate thermo: Run the smoker 10% hotter. I am smoking at 250 on my Chargiller Kamado with factory guage (it has a 10% variance so 225-275 which is fine in my book. but 225 is between 202-248 and 202 is way to cold to be smoking on.)
So just allow extra time is the big thing you will see.
Current Smoker: Char-Griller Kamado