I pretty much do the same as dorkfish.
I personally have a 20-gallon and a 5-gallon fish tank. I do my water changes weekly with a gravel vacuum. I siphon the gravel removing the fish waste (which isn't much) all throughout the tank. I used to take 8 gallons out of the 20 once a week. I'm now only taking four gallons out.
I would highly recommend a python siphon to anyone. You don't have to carry buckets, no spilling water, you can refill directly to the tank (then just add your water conditioner to the tank). The Python makes water changes much easier.
As for my five I probably take a gallon out, again once a week.
Weekly small water changes are much better for the tank than monthly large water changes. It's better to do 20 percent weekly, than 80% every four weeks. Even though the water amount is the same, the water can degrade a lot in a month, and then changing that much water can shock the fish. Some fish slowly get used to bad water conditions, some die from it. But if your fish are used to poor water quality and you drain the tank almost completely (and refill with clean chlorine/chloramine free water) your fish might not be able to handle the shock of the sudden change.