An observation on temperature control:
I think that paying close attention to temperatures is useful as a learning exercise.
However, once you've done a few long cooks, you'll develop a "feel" for how the cooker behaves -- how much fire you need for how long a cook, how fast the temps will rise when you open the vents, how slowly the temps will fall when you close the vents, etc.
I don't think that religiously holding precise temperatures like an oven is really necessary for good bar-b-q. I find myself paying less attention frequent attention to the probes during a cook and not really worrying about temperature swings.
Specifically, I will try to get the temps in the 225 degree range and set the vents for the temperatures to very slowly rise over a couple hour period. Often, that rise will top out in the 270 degree range by itself and then slowly start to fall as ash accumulates. So, I'll set the high temp alarm to 275. If the alarm goes off, I'll close the vents just a bit.
In short, as long as the temp is somewhere between 215 and 275 degrees, I leave the fire alone. Since the cooker prevents all direct heat, there is really no risk of burning up the food.
I start with enough charcoal for the length of the cook and am comfortable enough with the behavior of the cooker that I know the fire isn't going to go completely out.