On a day to day basis, usually. Sometimes I'll stick around later if I have a lot to do or I'm in the middle of something, but once I got my 80 hours for the pay period, I'm done and will either leave early or use the extra time for appointments.
Past that, I need to be approved for extended work hours. I've rarely worked over my 80, and that was usually due to outages or system upgrades, and I always got paid for the extra time.