Some of my best memories from around that age involve playing a computer game for close to 12 hours straight. I remember spending at least a month of summer playing through the Bard's Tale on the Spectrum.
Indeed, similar things have been a rewarding experience for me for the majority of my life.
Last time I did something similar was at the release of WoW: Cataclysm, I think, with my girlfriend. It was a great holiday.
Ditto. All-night LANs at our parents' houses playing Counter-Strike and other Half-Life mods, WC3, Starcraft, Diablo 1 & 2 in the basement.
Online games aren't all addiction and grinding and no-sunlight, there are an immense amount of social interactions going on. I attribute much of my writing skill to posting on internet forums with people I met playing video games, and chatting in-game.
I was counting up everything I'd gotten from playing WoW alone the other day, and it included a great relationship, a business that made me $xx,xxx, a whole load of new friends, experience and ideas for managing large groups that I'd never have gotten another way, LUA programming skills, some fantastic memories, and a major film project.