Re: How long did Nolans Batman actually fight crime?(SPOILERS)
It's "confirmed" he fought crime for 1.5 years before retiring (roughly 18 months between BB and TDK).
However, I'd throw out there that Blake said to Gordon, "the last confirmed sighting of the Batman was eight years ago...." I tend to think that given the process of getting legislation passed and then enacted, that things didn't get better over night. And I do think there had to be some ind of "freak" escalation after Joker for at least a year or so (Riddler? Penguin or Black Mask trying to fill the organize crime hole Joker and Two-Face left? Who knows even an eco-terrorist named Pamela?). So, I don't think it's hard to imagine he continued his crusade for at least a year or two or even three before he finally retired for good. It would explain why he bothered to rebuild the batcave in its entirety and why Alfred notes he hasn't been here in years (as opposed to ever if he hanged it up for good the night Dent died).
So, it's at least 1 and a half years that become 2 years when you factor in the months of TDKR. If you think he did more before the Dent Act cleaned up the streets, it could have been more like a combined 3 or 4 years. I like to think so, simply because the age of freaks Joker ushered in should have come in some form. Even in this semi-realistic view of Gotham. That is my take.
"Let us disappoint the Men who are raising themselves upon the ruin of this Country."