how often do you do water changes on your planted tanks and what kind of bioload does it have?If you have a small to non-exsistant bioload can you prolong the need for water changes?
Water changes provide nutrients your plants use remember, if you prolong the water change you are reducing the new trace elements that are introduced to the tank, they maybe minimal but it helps. Gives good clean water aswell, resets your ferts. I guess you could prolong it but why would you, water changes are beneficial they dont hinder.
It very much depends on the type of tank, high light tanks tend to need more frequent and larger water changes. Lower light tanks can be ok with less frequent water changes.