From another thread:
Originally Posted by ChrisBaleBatman
The only time I remember it mentioned that he hadn't been seen was from Foley said, when he told Blake after squad cars chasing Bane spotted Batman, that the "last confirmed sighting" was on the night of Dent's death. I don't know, I thought it still left room for some low key activity from Bats.
I don't remember Bruce telling Gordon that after Dent's death Batman wasn't needed. I'll have to see the film again to confirm, but I don't remember him even mentioning Dent's death to Jim in the hospital. He did say they'd won, which was why he retired.
But that's the thing...if there was any 'activity' after Dent's death, it was so low key and non-eventful that it's basically insignificant. So for all intents and purposes, he was retired for the full eight years. Aside from not being a 'constant' thing like comics, perhaps some fans see that as some sort of abandonment of duties...like it's somehow out of character for Batman. It's really not if Gotham didn't actually need him to take care of its major crimes...and as we see, the time off has not been kind, most notably because he does
seem to yearn to be Batman again.
So the circumstances of such a long sabbatical are different than the 'norm', but the character is still very much Batman because it hasn't sat well with him.