Talkin to some of the old fish heads I used to work with, they told me in the old days water changes were done rarely and or if something was wrong.Nowadays most keepers do frequent changes. Working at a pet store tho, I talked to people who never changed their water, of course that usually explained the problem they were having. With good plants to control the nitrates the only reason to do water changes is to regulate salt content. Tap water has small amounts of salt that build up over time from top offs for evaporation loss. Not a problem if you use r/o or distilled water.