In my 3 years of experience with WoW, 20 hours a week was a light weight. I've known very few WoW players, and I've known many, who were casual. For most, it was less of a game and more of a lifestyle. They even play when it's no longer fun to do so because it's simply what they do.

I'm speaking from personal experience. I kicked the habit. One day it struck me how I was always playing but was rarely having a lot of fun and I quit WoW cold turkey.

I now play other games with great moderation. I don't want any one of them to be come all consuming again.