It's probably not unique or novel and if I raised it in serious Bond circles I'd probably get laughed out of the room in the same way experienced by someone who went into a Trek convention with the theory that Kirk and Spock were actually women. (While espousing the theory that they were gay lovers would get you a booth to sell your fanfic.) Nevertheless, here it is. It's limited to the movies, of course, since I haven't read any of the novels.

Taking the movies at face value, James Bond has been in the spy business for over 40 years. He would be, at a minimum, the age of Sean Connery, which would tend to mitigate his killing power and babe-scoring abilities. (Not that Sean Connery has any trouble scoring babes, I'm sure. But I digress.) Plus, after so much success, frequent scenes with M taking him to task and questioning his actions would be ludicrous. If this were the same guy who killed Dr. No some forty-five years ago, MI-6 would just point him at the mission and stand back. But they're all James Bond, and James Bond isn't Doctor Who, so how can they be different guys?
My theory is that James Bond is a position, a job. Every now and then, the existing Bond retires or is killed, and a young agent is promoted to be James Bond, taking on all aspects of the Bond identity. I imagine it's an attempt to hide the real identity of the OO agents as well as to confound the bad guys, "But I thought we already killed Bond!" The new Bond does his thing for a few years and then turns the job over to the next up-and-comer. My theory is supported by the gender change of M in "Goldeneye". You can hardly claim that she's the same M, especially since Brosnan-Bond and M talk about her predecessor. If M has a predecessor, it seems that James Bond could as well.
The beauty of the theory is that it is completely consistent with what we've seen in the movies. After "You Only Live Twice", Connery-Bond retires and Lazenby-Bond succeeds to the post. After his wife is tragically killed at the end of "On Her Majesty's Secret Service", Lazenby-Bond quits the service. Connery-Bond is temporarily reactivated to bring down Blofeld in "Diamonds are Forever" and then Moore-Bond gets the job (which he unfortunately keeps for about 12 years). If you like, you can even make this work for "Never Say Never Again", though I wouldn't personally.
How does the new Bond film, "Casino Royale" play into my theory? Very well, actually, with one small change. They've been promoting this movie as "See how Bond became Bond". Clearly if this is the same guy, then either it can't be Bond's first adventure or the movie has to take place in the 1950's. However, if Craig-Bond has recently taken the job from Brosnan-Bond, it all makes sense; see how Craig-Bond became Bond. Woo hoo!
The only tweak to my theory relates to the 007 rank. At the start of the movie, Craig-Bond isn't 007 but he is James Bond. This suggests that the new agent takes the Bond persona and then has to earn the 00 rank. Which, of course, he does. If he doesn't, they get a new James Bond forthwith because no one wants a nancy-boy as James Bond. (Although they seem to have relaxed that standard from 1973 to 1985).
Applying the theory, it's fun to think about the various Bonds and whether they were killed in action or retired. My bets would be Connery, Lazenby, and Moore retired, Dalton and Brosnan KIA.
Anyway, that's my theory.









