Funny thing though about that- even though that WAS why, he still kept making Bat stuff, Like the exo suit, and the New Batmobile... but by then, his heart condition had gotten so much more advanced, ( and him even older, and probably out of shape,) that He couldn't USE the exo suit. I think the main reason that he was so bitter as an old man, was not only because of the Powers takeover, and the REASON he gave up the cowl- but because he COULDNT become batman again, even if he wanted to. His heart condition was pretty bad, just giving few whacks to some jokerz excited his heart.
The Exo suit was made before he quit being Batman. As for the Batmobile, we don't know when it was made, but since it interacts with the suit, it's possible it was also made before he stopped being Batman. Like Terry said, Bruce wouldn't have let a simple heart condition stop him from being Batman, and he's right.
Also, it's the fact that he winds up a bitter, lonely old man why I love the show so much. To me, it represents one of the truest outcomes of what would happen to Bruce Wayne.
And Bruce and Clark are best friends. Clark has quite alot of friends, from Diana to Jimmy Olsen, Perry White... But nobody he trusts with both his life and death. They may not hang out civily, and have a few arguments now and then. But I don't think there's anyone Clark trusts more in the world, in ANYTHING at all, than Bruce.
The speech that Bruce gives in the JL episode Hereafter is timeless.