WSM is dead reliable for temp control. Personally, I don't understand why people bother to put electronic temp controllers on these.
Here's what I did the last time I cooked a butt:
- threw some coals on minion-style at 10:30 pm, took best guess at intake adjustment. Went back to bed, set alarm for midnight
- woke up, tweaked wsm because it was running 25 degrees warmer than I wanted
- prepped butt and put on grill, stayed up for 1/2 hour to make sure temp was at 250 -275,
- back to bed, didn't check again until 6am. No suprise that the temp is exactly where I left it.
- had to take my daughter to preschool, so I left the WSM unattended from 8am to 12:30
- Once again, the temp was exactly at 250F
- I didn't make a single adjustment for 12 hours