My theory on Daniel is that he did his time travel experiment on himself, and he experienced the same things that Desmond did. The mouse wasn't capable of getting a constant, and died. Where-as Desmond did get his constant and well, he has presumably lived. So i think that Daniel found a constant, but still experiences the time switches, because whose to say that Desmond isnt going to keep going back in time, but now he has a constant, he can easily come back. After a long period of going back and forth in time, Daniels brain is basically becoming mush and he cant remember things because he's constantly living in both times. If that makes any sense at all
