Hey, my gastro said in "gastro school" they often practiced on each other! And when I kept refusing a colonoscopy and an upper endoscopy unless she did it w/o sedation and finally provided her w/that article I've published the link to several times here regarding pain during colonoscopy she actually underwent both scopes herself w/o sedation. She admitted to me that as I said the upper endoscopy was tougher w/o sedation than the colonoscopy becuase of the gagging.
BUT it takes more TIME for the gastro to do a colonoscopy w/o sedation, TIME they don't want to take.
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.