I have to say, chickens are not dogs, applying all kinds of psychology about spoiling is IMO over-thinking. You're not creating some sort of behavior you're going to regret. Is it a hassle to just add some water? If no, then just do it, no big. I do and I don't have a cut off age, they simply care less the older they get. Out in the coop chicks get water added to feed AND dry until integrated and then everyone gets water added when I see a bunch of powder under the feeder.
