It is always about balance. With years of having to use distilled water, I have work to do on my end when it comes to nitrates. So in theory, with ~70 gallons to the system it will take 14 weeks minimum to have all of that water out of the system with my ro/di unit up and running now.
But when it comes to water changes, it also brings with it the replacing of the calcium/alk/mag and many other trace elements that we can't even test for...at least on a hobby grade. Until corals are overwhelming the tank again there isn't a reason to even test let alone worry about dosing as the weekly water changes keep up with things on that end.