TFH had an article about this, I think in the spring. Basically this has been an issue of choice for decades. It seems there is one more opinion than there are people discussing the issue. The basic concensus was that 40%-50% weekly to biweekly water changes was good. The article did not discuss high tech EI dosing tanks though. I think you'd have to do weekly at least since we are dumping chemicals in the tanks.
There are commercial enterprises that also do daily water changes. I think it depends on how heavily stocked you tank is and with what type of fish. Like Apistaeasy said Discus have their own requirements.
The old adage was "dilute the pollute".
