We've always had to stay to the last minute, regardless of the situation.
Even on the day before Chusok when ALL the korean teachers left early, we had to stay till 4:40.
Even right before break when there was a big lunch with plenty of soju and beer provided, we were expected to come BACK to school, and warm our chairs for an hour. All through winter break, no camps, no students, no other teachers, just the english department in a freezing building.
Lucky ducks who get to go home early and/or "work from home"! We shouldn't complain, because then the few lucky ones might have their benefits taken away, and who does that help?