Why do my smokes always finish faster?

I'm about to finish 2 7lb pork butts. I did them at 250° on my recteq. from start to 165 and then wrap to about to be at 205° will be a total of only 6 hours... same thing happens to my briskets. a 12 lb brisket only takes me like 8 or 9 hours. they always come out tender juicy with nice bark so I can't complain. Just wondering why everything seems to cook faster. same thing would happen to me on my old pellet smoker too...