Welcome to the EGGhead Forum - a great place to visit and packed with tips and EGGspert advice! You can also join the conversation and get more information and amazing recipes by following Big Green Egg at:
It also depends on how much lump is burning when you decide to change the vent. I'll start my fire with vent wide open, and after the fire gets going, I'll adjust my vent to what I think should be right for, say 350. If the fire is large by the time I adjust the vent, I'll make the opening much smaller. If the fire is not so large, I'll adjust the vent to say half way. So it is about air flow, humidity, etc. but also about the quantity of charcoal lit... IMHO.
I built my own pit controller using Auber PID controllers. I bought 3 PIDS, one for the Pit controller and two more for temperature readers. If/when I get another egg, I can reconfigure and make one of the temperature PIDs a pit controller.
Fun project... Auber even provides the PID settings in the user manual for the PIDs. That being said, I didn't save a lot of money by doing it myself, but I am happy with the end result and suits my needs. It also is not blue-tooth nor wifi, you need your Mark-1 eyeball to check the pit and food temp.
The auber probes are actually K-type thermocouples, and have lasted for 3 years of weekly use.