I have been cooking at 240 degrees. My smoker has a built in thermostat and stays within a 5-7 degree window either side of 240. It is a vertical smoker and I have noticed that my top rack seems to cook faster. That is where I smoked the brisket. Even my butts take around 10-12 hours for an eight pounder.
Just trying to make good food for my family with a Masterbuilt 30" electric smoker