The thing about butts and really any of the larger cuts of meat is that they really are a crapshoot as to how long they'll take. Usually you can plan a certain length of time for it to get done but sometimes there is that little curve ball that it throws at you, (Fat Content)! The stall is caused by rendering fat releasing moisture which comes to the surface of the meat and acts like perspiration. Just like when we sweat and cool ourselves on a hot day the cooling effect of the moisture on the meat keeps the internal temp of the meat from rising, thus "the stall" and the higher the fat content of the meat, the longer the stall will be. So we try and power through the stall by ramping up the heat or by wrapping with foil or paper or both. I like to start a cook low and slow between 225 and 250 to get a good smoke on the meat, after about three hours the meat has taken in about as much smoke as it will take and then I'm going for color. When the color is sufficient I'll go ahead and wrap in paper and jack the heat to 275 which is really in between slow and fast but when combined with the wrap the moisture being released from the meat isn't allowed to evaporate and cause the stall. I usually cut several hours off of the cook this way and I have a very tender piece of meat when it's done because much of it's juices are retained instead of being lost to evaporation.
Never Trust A Skinny Cook!!!