How much?

At least half of my listening time is thru headphones, not at all the same but at least something.

terry9, I take umbrage at the statement "The other posters are listening as background music."  Is there a 2-hour-per-week limit to serious listening?

16 hours a week 

I still do important things...I just put new strings on a guitar, the motorcycle won't ride itself! And my medicare pays for the gym membership so I gotta go at least 3 times a week...I have spent a lot of time recently listening to my cables breaking in...sort of a zen thing, and they were exactly 3.7% better sounding today...this stuff takes time man...riding my "longboard" skateboard down my street without spilling my beer isn't so easy either, and may explain why my neighbors won't talk to me.

I'm also retired/disabled.  I will listen to music for over 10 hours on some days when I can't leave the house.  Some days I'll only listen for a couple of hours.  I do listen on the go with my custom in ear monitors (Phantom's from Empire Ears) with my AK380cu and matching amp, lol.