Don't get me wrong. You can open the door if you are cooking items that finish at different times. But, if you are cooking one piece of meat you are typically going to be going by Time or Internal Temp and you would not need to open the door.
One thing that you will find is that these smokers take very little wood. In fact, you will want to invest in a digital scale if you don't already have one because most smokes under 6 hours will use only 2-3 ounces of wood. You would use 5-6 ounces for longer smokes like butts and briskets.
We all have come to embrace what we call around here "Lazy Q". Instead of babysitting our smokers, we set them up and watch them with a beer in hand or go about our business until the thermometer timer goes off and tells us that the food is ready. I often times sit at my table next to the smoker with a beer and just enjoy the beautiful blue smoke that wisps from the hole in the top of the smoker. This is making me wish I wasn't at work and at home smoking something.