Why is it necessary to insinuate that the guy doesn't know how to maintain his batteries?
A surprisingly high percentage of exchanged batteries actually did not fail at all. Besides the crook above who just exchanges them for no reason at all, you have folks who will immediately buy a battery when their car won't start, without checking their charging system and cables. And maybe a second time when that one goes dead, before they figure out something else must be wrong.
We had a used battery shop here in town that made this fact their business. They collected used batteries, pulled off all labels, pressure washed them inside and out, spray painted the jars, and replaced the electrolyte. Give it a 6 month warranty and hope for the best. I have no idea of the percentages, but it was enough to make a business out of it. Environmental restrictions put them out of business.