3 should be no problem on cook time. Especially if you are doing it on a larger cooker like a UDS. I do 6 butts on my drum and it takes a good solid hour to get back up to temp after I put the meat on. If I really need to keep a tight schedule, I break up the work load and do 4 on the drum and 2 on the Pit Barrel. Less recovery time on the temp with a little more cook management is a good trade off with me. 6 Butts on a single UDS can become a bit cumbersome, especially if you are wrapping them to beat the stall and stick to a schedule.
18.5" OTS, 22.5" OTG, CB Silver(Rip), Vintage Coleman Bullet, Pit Barrel, UDS