On weekdays, I try to play about 45 mintutes to an hour and a half [plus another hour for the Internet]...but that varies a lot since I don't really get a consistent number of homework everyday- somedays I have a lot, others next to nil. But when the weekend comes along, it is a whole 'nother story: play all-night on Fridays, and blow off my Saturday with almost non-stop gaming/Internet; homework can wait until Sunday

. All in all, I manage my time quite...uh, effectively, one way or another, and for good or for bad.
As for grades, I've managed to keep an average GPA of 3.5 (Math and History can go to hell) despite lack of sleep in last-minute-projects and relatively long gaming during the week. For sleeping hours, I try to get at least 8 hours, but mostly sleep only 7; sometimes 6. But all might change next year, as I'll be slammed with foreign languages, economics, and health.