I believe that it has been stated by DiDio and Lee at various times that yeah as OdoWan pointed out, Batman has been the hero active the longest, having been operating as a myth and "off the radar". This was pretty much confirmed during his first meeting with Hal in Justice League #1 when Hal incredulously states something like "I thought you were just a myth!". I believe that Dick and Tim have been deaged as well in the new time line to explain the Five Robins thingy. Damian is ten years old, his conception (Son of the Demon which I believe has been made canon again) would have to be during Batman's early years...like year two or three even and way prior to the "five years ago" start of the new timeline.