I do 20-50% every 2 or three weeks.
I have a remote sump, so my life is pretty easy.
I have a 150 mixing tub that I pretty much keep full of saltwater ready to go. There is a modded mj in the tub for circulation, a 250 watt heater and a powerhead just for aeration. The tub is hooked up to my RO system with a float valve, so when I need to fill it, I turn on a valve and the float shuts of the water when done.
There is also a pump in the tub that has a line leading to the sump. This pump is on a float switch in the sump, so that when the water change is done, the pump goes off automatically if I forget to shut it off.
To remove water form the tank I put a line connected to the closed loop into the toilet which is right near the back of the tank, and turn the valve on. About 7 minutes later I turn it off, run downstairs and flip the switch on the fill pump in the mixing tub and voila. I came up with 7 minutes by putting lines on the sump at 10 gallon intervals, and 7 minutes is about 50 gallons.
One day when I am super bored I will plump the drain line from the closed loop pump to a drain under the house and then I won't have to uncoil a line to the toilet. This would make life fractionally easier, but not enough to get me to put it high on the priority list.