when does a water change become irrelevant

[Aquattro]

Originally Posted by Proteus

Just makes me feel as if it's better water

I agree. But this then suggests you think the water in the tank is of lesser quality?
I'm certain of the fact that changing water does no harm (with exceptions of course) and I notice the tank does better than any previous tank I've had where I did less frequent changes, so for me, it's the most important thing I do.