I generally don't have a lot of business in my dedicated office hours, but then sometimes I get a needy student who wants to use all of them -- every minute, of every day, in which I hold them. It gets physically tiring for me, and emotionally draining that they apparently have no capacity or confidence to follow along in class, read the book, or make connections on their own.
Granted that we have, say, 3 hours of office time per week (required at my institution), is it acceptable to set per-student limits on usage of that time, such as: 20 minutes per student per day?
Additionally, is it advisable to be forthright and tell the student that their behavior is unusual/a bad sign/an abuse of the office hours; that is, that they should be mostly responsible for the material on their own? (Often this same type of student will praise themselves aloud for being so proactive/smart with the office hours when others aren't using them.)
This is in the U.S., and I'm at a large urban community college. Assume that most of the time no other students are showing up to the office hour.
(This was mentioned in this question and comments therein; I'd like to see a canonical answer on just this aspect of the situation.)