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If you go by everything we now know, it may be that Bruce hung up the suit in hopes that Terry would take it up one day, since he knew Terry was his "son".

I think partially Bruce had to hang up the suit because he just could not do it anymore, even with all of the modifications to his suit, he could not combat the fact that he was getting older, and the criminals were getting more advanced.

i thought it was because he was haveing heart problems in the first episode he was clutching his chest like he was haveing a heart atack.

From what I know, this series goes off a quiet bit of what the Graphic Novels do but at the age of 46, is when Bruce Wayne Retired as Batman, due to his heart issues and the fact he was getting to old to stop crime. Not to mention he wanted to settle down on life and The Authorites thought him to be another criminal.

Now if you watched episodes like rebirth, epilogue and rotj,you would know this. he was getting too old yes, but he didnt realize it until his fellow heroes and sidekicks abandoned him, and when he almost killed/used a gun.

In one episode, Terry says to Bruce "someday, you're going to tell me the real reason you stopped being Batman," after Bruce said it was due to his health conditions

My point is, I remember reading a theory that that real reason was because Batman had to resort to pulling a gun on one of the criminals in order to survive, something he never did before. Seeing that that was what he had become, he gave up the Batman identity

I pretty much agree about that where Bruce retired due to having to resort to using a gun on a thug so he wouldn't have been beaten to death.
But as far as the suit goes Bruce needed the extra strength [which amplified the user's strength by 10x].

Agreed

The beginning of "Rebirth part 1" answers the question, but JLU's "The Once and Future Thing part 2" sheds new light on the question by having Bruce travel to the future to meet Terry.

Bruce quit cause he didn't have the strength he used to have, his age, and the fact that he had to stoop down to the level of the common criminal to live which was something he never wanted to do

Yeah, that was my point as well, about stooping to the criminal level. Batman believes that what separates him from an actual criminal is that he doesn't kill. Furthermore, he vows to never use a gun. In the episode, he had to not only use a gun as a last resort, he had to threaten murder with it. I believe that in spite of all his health problems, this was what he could not stand and this was what forced him to hang up the suit

i wish he used the giant metal suit or had a legion of bat robots
like in kingdom come