Virtual office hours can be held any time and instructors can set the office hour channel up so that a tone indicates when a student enters the channel. No one has to sit around and look at the screen while waiting for students to visit. Faculty can hold office hours from home or their campus office.
Office hours can be scheduled for a predetermined time on a weekly basis or a time agreed on during email correspondence.
An added benefit, as with any IRC communication, is that the conversations can be logged.