I've never smoked brisket overnight. The reason being you don’t “set it and forget it” with brisket. Normally with a longer smoking session like brisket I will tend to it every hour during which I baste, mop, or spray the brisket to keep it moist and add flavor. I will also check fuel, water and hardwood to see that supplies are enough to last through the next hour.
If you wish to try an overnight smoke with little maintenance through the night, you might look into the “Minion Method” for firing your smoker. http://www.virtualweberbullet.com/fireup2.html
If while using this method, your smoker gets too much oxygen, you could have 400-500 degree temperatures after bedtime. The first time I used this method the temps started to climb and I had to completely close off all three vents on my smoker for two hours unit they started to drop back within target range (225-250). The total burn lasted for five hours (I was cooking chicken and only needed 4 hours). Depending on the smoker and the amount of fuel used, you can have longer times, they say up to 16 hours. I would strongly recommend practicing during the day with long burns like this prior to leaving unattended at night.
The best way to get constant temperatures is by regularly monitoring them.
Starting a fire; be it a smoker, stove, fireplace, or even a candle at home and leaving it unattended while sleeping is extremely dangerous and not recommended. Be very sure that your smoker is safe from being knocked over by winds, animals, etc. which can start secondary fires. We don't want to see any of our board guests on the news unless it's for award winning BBQ!
Hope this helps.
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