Hehe... Seems the pork butt fat discussion is as lively as the "fat cap up or down" discussion on briskets! Love it! That's what makes this so fun - everyone has, and passionately defends, their techniques.
Ginger - allow for 2 hours/lb, to be on the safe side. Don't get a butt less than 7 lbs, either (they cook very unpredictably). I, personally, use 1.5 hours/lb, because I've never had one take more than that. That's because I buy my butts from the same place, so the quality of the meat is always similar...so they "behave" the same!
That's a tip, btw... Buy your meat from the same supplier, every time, and you'll get more consistent/predictable results.