I had a real problem in my teens with the PC game Sims 2 (which i still love now but rarely play it!).
At its worst was the summer holidays when i used to get up around 10, straight on the sims until 12. I would stop for 45 mins (dad would pop back during his lunch break and go on the computer). I would then go back on it until around 4. Once my parents had gone to bed (around 9) i would be on there until at least 12-1am or even later.
That was pretty much every mon-fri. I cant remember ever feeling like it was too much but now i look back in horror at how much time i sat playing it!
I can easily see why people become addicted, especially younger ones.