To be honest, I don't intentionally do any water changes.
I end up changing about 5 gallons per month, as a result of cleaning out my canister filter where I run activated carbon. Every two months, i swap the old GFO for new GFO in the reactor, and change a little water by letting the reactor run clear. Those are the only ways in which water leaves my aquarium.
Yes, I know water changes are beneficial for many reasons, I've read Randy Holmes-Farley's articles and all that good stuff. They're just inconvenient for me, and the tank looks great, so I'm sticking with my routine.
My bioload is 2 oscellaris clowns, 1 royal gramma, 1 blue damsel, 1 filefish (for aiptasia control), and 2 little scooter blennies.