Ah, and there's the issue. You NEVER have to worry about drying out a pork butt because it gets it's juiciness from melted collagen, the tough fibers of a hard working muscle. If undercooked, it will taste dry and tough because there's too much collagen remaining. If overcooked, it will be juicy but mushy because all the structure has melted away. A pork butt isn't a loin or a loin chop. Those get dry when overcooked, thus their internal target temp is around 140-145F and you DEFINITELY have to use IT to get a juicy chop or loin.
The sweet spot for a butt's IT when the meat is going to be pulled is generally between 200-207F, but it can be a little less or a little more depending on the animal and how it was raised.
Max temp? Next time you smoke a butt, aim for 203-207F IT, but start probing at 195F, purely for education purposes. Probe every 45 minutes or so and take note of the IT. You'll quickly get a feel for how the meat softens FOR THAT PARTICULAR pork butt as the IT rises. The next butt you do may be totally different. And many times I've had two butts of the exact same size finish hours apart when smoked simultaneously in the same smoker.
Another thing to remember. Heat is transferred to the meat faster the greater the temperature difference between the meat and the chamber. If you're smoking at 225F and the final 10-20F IT is taking forever, that's physics. Crank up the chamber temp another 50F to increase the difference. Trust me, that butt doesn't care one bit.
Happy smoking!
Ray