Waaaaaaay back in the day I used to rent games from the local video shop, so I had to go through most of them in one sitting (back in the Master System days). One day I rented Wonderboy Dragon's Trap and it almost killed me. I stayed up all night, paused it for a couple of hours while I went to a job interview, then came back to finish it. These days I could probably finish that game in a few hours, but back then it was a huge challenge. Now I'm older I won't play any game for more than 2 hours (except Left 4 Dead or something where it would let down the team). I just lose concentration and, more importantly, enjoyment, after about an hour and half.