I am getting ready to smoke my first pork butts. They weigh about 5-6 lbs each. I've read all of the charts and am planning on 1 to 1.5 hours per pound (or longer!) at a cooking temp of 240F. I plan to wrap them in foil when they reach between 140 and 150. About how long should I expect it to take to reach that temp? I know it needs to less than 4 hours, but don't know what to expect.