I had a similar experience with gaming, but with Civilization V, Dwarf Fortress, and other RTS games. They felt enough like I was "working" that I didn't care/notice how much time I was wasting each day. Now I've moved on to the same work-then-play mentality you described, but even then I try to replace gaming with reading or creative projects.

Watching my own sense of purpose change as I've gotten older has been interesting. I used to have a carefree (and careless), go with the flow personality. In the last two years I've become achievement and goal-oriented. I think it feels much better to have a reason to get up each day.