I get a new game, play it flat out and get fairly far. Then I stop playing because Im bored of it so I shelf it till Im keen again.
When I start playing again(months later) I finish it in an hour or less because thats how close I was to the end and Im left thinking 'is that it?'. Its happened now with Half Life 2 and Saints Row 3 this week both awesome games but the overall impact of seeing the credits roll has been lost.
I call it Gaming A.D.D. or Gaming Schitzo.