That would be true but there is a way to cheat with charcoal or stick feed smokers. you can add a digital temperature controller that in trun controls a stoker fan. When the temp lowers the temp controller senses it and turns on the fan to stoke up the fire when the temp rises the fan turns off. You can buy them all done up as a system or if you're handy you can even make your own like I did.
Here's one to give you the idea.http://www.rocksbarbque.com/index.html
It was both too expensive and too fancy and over the top for what I wanted so I took the DIY route.
It cost me all of about 50 bucks if even that with parts I ordered from China, some found in my junk box and some from a local salvage store. It's not hard to do so if you want to give it a try I can give you a hand and tell you what and where.
I like making my own stuff anyway. That way I know what's going on and how to fix it should something go awry. Plus it's another excuse to tinker.