I've been playing with ARs since before I bought my first one in 1989. I even worked briefly for an SOT building M16s out of old Nesard parts kits. I've never personally run across a gas tube that was clogged by fouling. I have run across several gas tubes with those long fuzzy pipe cleaners or various other foreign objects stuck in them and stopping function.
I do not clean my gas tubes at all. If I replace the barrel, I'll replace the gas tube. My thought is that if 15,000-30,000 psi of hot gas after every single shot isn't keeping the gas tube clean enough, I am not likely to do any better with a long fuzzy pipe cleaner.