Steve - I would not worry, since you asked. Get a good remote meat thermometer for the big stuff - butts, briskets, whole chicken/turkey, etc. and cook to temp of your choice. For ribs, figure 4 to 6 hours. I have had butts finish in the 11 hour range and some that went 15 or more. I don't know why. I have suspected that the meat probe in the butt/brisket was securely anchored in muscle but was also in a fat pocket that after a time rendered out leaving the tip in empty air. Thus the long time for a cook. Always good to have an instant read handy.