I disagree. I don't think that he's on Batman duty every single night with those 8 years being "peace time" and the GCPD still hounding him but I don't think that he completely retired during those 8 years. This is a Bruce that needs Batman more than Gotham needs Batman.
I agree, but it's not like an obsession. A serial killer needs to kill. Being Batman helps Bruce cope with his issues, but I don't feel like his this compulsion like a serial killer has when he's sucking life out of a human being.
Bruce will certainly be out of commission for a while when Bane defeats him. Gordon might be alluding to that.
After Bane defeats Batman, he is in total submission. He grows a beard and is stranded in a cot, it looks like. Though it's hard to tell from the teaser, he does not sound defeated (the adjective that comes to mind is conflicted). I submit that Bruce becomes Batman, confronts Bane, gets messed up, ends up in the prison, and trains for his comeback in prison. You can clearly see Bruce doing PT in a prison cell in the teaser. He makes the decision to bounce back from his defeat while in the prison, not seeing Gordon on his deathbed.
EDIT: Also, the dialogue makes it sound like he's been gone a while.
Gordon: "We were in this together, and then you were gone. Now this evil... rises. The Batman has to come back."
Bruce: "What if he doesn't exist anymore?"
That dialogue suggests a leave of absence if you ask me.
He has a new and improved Batcave, a new toy (LED gun thingie) and The Bat.
He built the Batcave relatively quickly in Begins, it wouldn't be a stretch that it gets upgraded over the course of TDKR. Also, I imagine the damage from the fire in BB was minimal, so once Wayne Manor is rebuilt, getting the cave accessible ought to be a cinch.
As for the new gun, it too could be designed over the course of the film. Also, just because something is used by Batman for the first time doesn't mean it was built in between films. Wayne Enterprises might have built it before, hell, even BB takes place. It just hasn't been practical for him to use it.
The best argument you have is for The Bat. This thing probably would have been used already if it had been built. But I still contend Batman's suit is the same, and he hasn't replaced the Tumbler. I just don't know why those things wouldn't have been taken care of over the course of the eight years if he were active.
He started out being Batman even without someone like The Joker as an opponent. And who's to say that he wasn't fighting someone like the Joker during those 8 years
You're right, maybe there were a plethora of Bat adventures between the eight years. It is a wonder, if that were the case, why Nolan decided not chronicle them in film.

Also, yeah, Batman went after the relatively unexciting criminals in his early days, but the stakes were low. Would you go after a Maroni or Falcone if you knew the stakes after the conclusion of TDK?