During the 60's-70's....fledgling US Army helicopter pilots did EOL's as a simple matter of course. I can recall some flight periods that were devoted to nothing else....one right after another and another and another....until they became second nature. The engine remained at idle throughout the maneuver from the time the throttle was rolled off until it was rolled up again during a before takeoff check for the next circuit. There were contests (very informal and most unapproved) to see who could slide the longest distance...who could land closer to a predetermined spot...who could hold the bird at a hover without engine power the longest.....all of which taught one the ability of the UH-1 (Bell 204/205) to perform in autorotation.
Autorotatations were stressed because of the very strong likelihood you would be doing some in anger within the next year while flying combat in Vietnam. FOD, in the form of 7.62 - 14.7mm lead pellets was a very common happening there....in addition to the normal rate of engine failures. It is reported that at one time, there were over 7,000 helicopters operational in Vietnam.