I like the idea that Jack's immortality was a trigger for the hard regeneration from Nine to Ten, but not sure I agree with the sentiment that he wandered off (unless using that as a euphanism for getting himself killed) since he was battling the daleks in order to buy the Doctor enough time to build the Delta wave.
Author's Response: I guess that didn\'t come across very well. What I meant<\\i> was that however long Jack might have waited on the game station in his own timeline, in the Doctor\'s he was waiting on Earth when he arrived, and had changed a hundred years of Earth\'s history in the process. If he\'s gone anywhere else it might have been a different matter, but the Doctor now couldn\'t retrieve him without crossing his own timeline.