Anywhere between 6 to 10 hours a day. Almost my whole work day is headphones on... plugged into laptop...
I run around a bit and help users... most days majority is at my desk. Get home, ... computer goes on. Gaming and listening to tunes, then movie while I work, then crash to either music or movie.
I don't think it's a bad thing, but then maybe it's a problem? My coworkers just got used to it. They throw things at me or text when they need me, even if they're 5 ft away. I'm sure I would've heard a lot of hell about it if I weren't good at what I do (which is IT nonsense).
On weekends, maybe 3-4 hours. Usually with the woman and more movies or doing whatever she wants to do.