I voted sometimes, but really it's almost never, unless we're talking about a game with a four hour or less campaign. There's two reasons for this. The first is simply that I either get bored with a game, or buy a new game that I can't wait to start, and wind up getting sidetracked into another game. The other is, if I enjoy the game, I feel like I've gotten my money's worth whether I finish it or not. This could come down to my formative gaming years coming during the era of limited continues and no saves, wherein beating any game was a sign of true godhood at gaming. It's also affected by the fact that I never buy a game at full price unless it's a limited release from a small studio, which I won't be able to find if I don't get it while it's new.