Ok, having turned on the parental control to kill the realID thing, I now have an easy way to keep an eye on my play time. Problem is: it's not play time which is measured, it's connection time. And when you have the habit of leaving your character logged in when eating/cleaning the apartment/etc. the two can diverge. But how much?
So I decided to do a test: instead of leaving my character around, for one week I decided to log out immediately every time I do nothing. Of course dungeon finder queue time, which I spend doing something else, will still be there, but that's small compared to the rest of the afk time. I also had some AH afk going on, but less than usual.
The result was surprising. I usually hover at 30-33 hours/week (1800-2000 minutes), this week I was at 1520.... That's 6.35 hours less "playing" than what I thought (even without parental control I always considered 30h/week).
It looks that I'm more distant from the "heavy duty hardcore" threshold (45-48h/week) than I thought! I'll have to play more :)