Mike,
Draining the front hub oil through the drain plug in the front hub cover does not get all of the oil out, but you get 2/3s to 3/4s of the oil out, so you are not doing a complete oil change, but it is quick, easy, and cheap. To get all of the oil out, you have to remove the front hub and rotor assembly and lay it face down to drain all the oil. When I changed the front hub oil in my coach at about 135,000 miles, I removed both front hubs, drained all oil, replaced both front brake rotors, replaced front brake pads, and replaced both front hub oil seals.
If you change your hub oil, only use a full synthetic oil.
Gerald