I'm having a large family and friends BBQ 50/60 people on Saturday, I've ordered 3 10lb briskets and 3 boston butts all to go on my Yoder YS640, how much extra time would all this meat need to cook. I was thinking of throwing it in at 3am to be ready for 5/6pm.
Personally, I would calculate your required cook time, given your desired cooking temperature, and add 2 to 4 hours on to it. Brisket and butts benefit greatly from a long rest period, and the quality of the end product will not suffer at all, and most like be much better. To rest, once the meat has reached the desired tenderness, let the meat cool for 15 minutes (vent the foil if you wrap) to stop the cooking process, then wrap in foil, wrap in towels and put into an empty ice chest (cooler) to rest until you need to carve/pull and serve. I do this all the time, and have purchased a large Cambro instead of using an ice chest for accomplishing this.