Does anyone know what the relation to a drum that has some "seasoning " to it versus a squeaky clean drum. I have been finding that with my Hottop drum if I get it to "clean" then it prolongs the roast and throws my times off. It takes 15-25 roasts to get it back where it seems to retain heat better. It also has a definite affect on the quality of roast. Any thoughts on how much to clean the drum?