I believe Qui-Gon was originally intended to be sixtyish, but have the impression he was made younger when Liam Neeson was cast in the role... but I suppose I thought "clean living and the 'light side' of the Force" when I first saw the arrangement of birthdates (and then thought of how we eventually learned Ned Flanders is older than he looks)... All in all, though, I have no idea where this little timeline came from, and don't intend for it to shape my opinions from here on.