When I have time or if I'm up to playing, approximately an hour or so at a time, maybe once or twice a day.
And if you want an answer according to the in-game playtime tracker...15 minutes.
I am the one who knocks.
Since the Subway beta I played it for 7-10 hours a day up until about a month ago and since then my play time has dropped to an hour or two a day if I even get on UC3... Trophy hunting is more fun than screaming at the TV because of lag and all the other BS this game has.
In total I've played it about 650 hours including both betas.