Playing devil's advocate here, but if his child-hood friend who he planned on being with when someone took his place as the city's hero died, his chance of a normal life died too. He could have potentially fallen deeper into the persona of Batman and accepted his role as protector.
In fact, I thought it was a shame that the name "Batman Forever" had already been used by a subpar movie. I thought it'd be the perfect title and a perfect ending to the trilogy to have Batman finally get a grasp on his role as Bruce Wayne and Batman. After the film, I thought we'd get an ongoing series of films like James Bond. Recasts, new directors, new production design, etc. When the title was released, I looked so far into it that I viewed it as a knight rising after he is knighted by a king. I thought the city would kind of accept him as their masked vigilante and tolerate him after believing him to be a murderer.
Obviously this is not what happened. I think the above situation would have been embraced by the haters because it's true to the comic Batman. But as you mentioned, Bruce was looking for a way out the minute he signed up. He said he'd do it "as long as it takes." His mission wasn't to fight crime and avenge his parents' deaths. It was to "inspire the people out of apathy." He wanted to take down the mob and remove the criminals/corrupt from the government. He wanted the city to become like cities today where people could turn to the government and police for help and protection. Prior to Batman's arrival, you couldn't do that and people lived in fear everyday. This is a totally different take on Batman. But if you pay attention to the details, TDKR finishes the mission as seen in BB and TDK. We didn't pick up on those details the first dozen viewings because in our minds, Bruce is Batman forever. I believe Nolan did a great job with the first two leaving his take on Batman so subtle that if he chose not to do any sequels, he didn't shoehorn his vision/direction onto any other directors. And by forcing them to reboot the series, no future endeavors will take away from his narrative. Fans will hopefully get their comic version of Batman and the Nolan fans will still have this version.