Put another way: that leaves 10 hours a day for eating, sleeping, and the actual things that make relationships work (quality time, sharing responsibilities, etc.). Unless your friend didn't sleep, he probably wasn't being a very attentive partner.
Makes a great guild leader though?
I have found that average number of hours played per day is negatively correlated with how laid-back the player is. Laidbackness is bimodal, in that lower skill and very high skill players tend to be laidback. A large amount of above average (but not excellent) players tend to play more hours per day, be more obsessive, less forgiving, and fairly judgemental of how other people play. I like to think of this as the Dunning-Kruger curve in action. We call these players "sweaties", because they are breaking a sweat and stressing over everything. Really great players don't stress, they just perform.
The newest Doom games are great, but there is no deep story, just enough plot and lore to give the game context. In a practical sense you're shootin, jumpin, and clickin -- 20 frenetic minutes of excitement. Put cursor over target until dopamine is deployed, repeat. Crazy adrenaline highs but also no larger engrossing activity except generating skulls for the skull throne.
-John Carmack