Sometimes people just want to work on trees. it doesnt always come down to impatience when someone overworks a tree or pushes it a bit hard, sometimes they just want to do bonsai work. on mediocre to cheap material i dont see a problem with that really.
there is a saying that goes, 'if you find yourself doing too much, at one time on one tree, go buy more trees' work on those instead. there you go. if you dont have money to buy more trees, you might find yourself in a bit of a dilemma until you do. because it can become a very boring hobby if you dont have many trees and you've done all the required work on each one, in those situations you might find yourself doing more than necessary, im not gonna knock people for that.
i love working on my trees at anytime i want to, therefore i only usually work with species that can take a battering, thats just me