I agree with everything idahomike said. On my sm066, the deviation from the set temp is never more than two degrees once the slight overshoot on startup is done. One caution: on a very short cook like fish, by the time the startup is done, your fish will be more than halfway there. As an example, I smoke 8 oz. salmon fillet pieces at 200F looking for a IT of 140 - 145. When the smoker settles in at 200, the fish is usually already at 90 - 100. As idahomike said, overnight cooks are easy once you figure out the temp and timing sequence.