For me, briskets always take longer than butts for some reason. I typically cook at 225-230 and can usually estimate 1 and 1/2 hours per pound. Butts will be done about 30-60 minutes before briskets will but in the grand scheme of things this really isnt that big of a time lapse.
Blue Moon Porkers
FEC100 / GMG Jim Bowie (Dealer)/ Sams Club Gasser / King Cooker Hot Tub