This is a great poll! I usually finish just after midnight. If I'm getting close and it's late...I just keep going, and that is always in the wee hours.
After midnight is pretty common, since my play time is usually limited to late nights or weekends but I'm not still up playing games at 5am, 2am is about my absolute limit.
No specific time but 100% guaranteed the wife will walk in and ask me to do something just as the final cut-scene is going on. Then I've got to look like an arse and say 10 minutes more dear.