I think that for a seasoned weight lifter that has gone through thousands of workouts at a very high intensity of work, lifting very heavy weight week after week year after year reaches a point where progression is very very slow and recovery from those workouts take longer to achieve, I find myself reducing the intensity whereby I'm just doing a maintenance type workout every fourth session.
if I don't give myself time, I become very tired and irritable and such, muscles start twitching all over, lose my appetite, and my HR increases.
I've also noticed that after a break of more than two days between workouts, I'm totally ready to go, and smash previous bests.
I have a choice to either do a lot and often, less intense, or what I'm doing now, but because of my make-up, I hate doing the former option.
I've been approaching this option for the last 25 years, and I do feel the over-training is a real thing and more common than people realize.