You were looking for:
You, Too, Could Be Batman In 10 To 12 Years
Continue to the story"You could train somebody to be a tremendous athlete and to have a significant martial arts background, and also to use some of the gear that he has, which requires a lot of physical prowess... In terms of the physical skills to be able to defend himself against all these opponents all the time, I would benchmark that at 10 to 12 years." The problem is, even after that amount of training, no one could remain on top of their game for more than a few years. And "Batman can't really afford to lose. Losing means death - or at least not being able to be Batman anymore."