Re: Batman retiring...
Warbler, did you ever read The Dark Knight Returns? Dark Knight Rises is basically a modified adaptation of a lot of the elements in there. One of them is that Batman disappeared for ten years, and at the start is an old man with a ton of health problems, and he knows that if he choses to get back in the fight he will die, because his enemies can physically best him (one giant brute really cleans the floor with him, and he has to be rehabilitated). He nearly does get killed, it's quite a brutal battle, and as his last act he fakes his death so that he can retire and pass the mantle on to a team of apprentices to continue the symbol. So that element is in the comics. Not the "golden age" interpretation, but the Miller interpretation, which is what Nolan based his series on.
Realistically, Batman has two options: 1) Fight until he dies. 2) Retire. His body is riddled with health problems. He has no cartiledge in his knees, elbows and shoulders, his kidneys are covered in scar tissue and he needs a futuristic leg-brace just to walk around without a cane. Then he gets his back broken on top of it all. How long can he do this before he dies? And if he doesn't fake his death in a blaze of glory, as a martyr, would he be of any effect if some punk in an alleyway shot him in the face and left him in the gutter because Batman was a 40-year-old cripple who couldn't move fast enough? At the beginning of TDR, we see that Bruce can't do it anymore, and by the end of the film it is clear that there is no long-term future for Batman because of Bruce Wayne's exponentially increasing health problems. That punk in the alleyway with a handgun may be a day away or a year away, but the day when Batman meets him is within striking distance. He has to either die or give up while he can still be a symbol, and blowing himself up with a nuke to save Gotham is the best scenario that will likely come around in the next couple years before Batman gets killed in an undignified homicide.
Chris Nolan was trying to adapt the Batman mythology--because it's a mythology, with fluidity and variation and without a single source or canon--in the genre of a realistic crime saga. "If Batman plausibly existed in a real world setting, what would it be like?" Frank Miller tackled this in his books, like Batman Year One and The Dark Knight Returns, which is the "source" that Nolan used. Miller's was a bit more fantastical, being a comic book, but for a realistic crime drama movie would seem absurd and betray the reality the story is otherwise composed with. Things that work on the comic book don't translate to the screen when you just literally translate, which was the problem with Watchman, it didn't account for the realities and experience differences of the two mediums, it was too faithful in many ways. That's why you adapt source material, in this case taking Frank Miller's work and placing it in a realistic modern environment.
Anyway, bottom line is that the Batman of the comic and "the source", as much as one can say so, for Nolan's trilogy, which is Miller's work and in particular DKR, does retire, return, get killed in battle, and then retire as Batman again once we realize he faked his death, witha replacement in line to carry on the legacy. Nolan gave Wayne a more uplifting ending, but there is ambiguity about it in terms of whether he is gone for good or just taking a much needed rest before he returns to the Bat-cave to mentor Blake.