Well I guess the best solution for these types of games is making them episodic, but unlike Valves example with Half-Life. You have a well planned out game with DLCs that come out on a timely bases, and unlike some DLCs, you're not getting material that suppose to come mid game like Mass Effect or Fallout.
For example take Heavy Rain, the DLC that comes with the game is some mid-game material, and the question is what's the point of it if we've already beaten the game and in this case solved the murder mystery?
Heavy Rain should have been an on going process like a TV drama, where episodically we'd get tid bits to the murder mystery, hell if it was done like this we could have had the "who shot JR" of video games.
Alan Wake should also take this example, and if the game concludes after the 8 hour mark, the DLCs just won't be interesting. It'll just be like the second half of the second season to Twin Peaks when the murder mystery was solved, and the reason I bring up that TV show from the early 90s is considering how heavily this game is suppose to be inspired by it.
Did the developers learn anything from the mistakes made in Twin Peaks when the ratings dropped and the show was canceled?