Anyhoo, thanks to my experience thus far, here is my list of signs that you have been playing Fallout 3 for too long:
7. Your finger is sore from where it rests on the underside of the controller.
6. The sides of your hands are sore from where they've been resting on your lap as you hold the controller.
5. You go to bed because you are tired, and know that sleeping will bring your health bar back up to full.
4. You begin to look at objects around the room as though they are items that you would consider picking up to sell.
3. When you approach a light switch you expect to see a prompt asking you if you want to "activate" it.
2. You begin judging plots of movies and TV episodes in terms of what parts would be made into quests, and what the quests would entail.
1. You sleep poorly, because you keep being woken up as you finish parts of an entire quest that you complete in your dreams.
That's only seven. Maybe I'll have more after I play longer. Oy.
Oops. I need a picture. Here's a poster from the game:

Oh, and did I mention that Liam Neeson does the voice for the father? That alone gives the game big bonus points.