50 is the new 30....In NASCAR when does age come into affect?

You would think that if your over 50 then it would be time to retire from racing but, one driver has brought the whole age thing back. Given a rocker back in 2005 calling it his last hoorah we all thought does this mean that when drivers get up there in age the driver ponders the thought of calling it quits like dale jarrett & michael waltrip but when we all thought that Mark Martin was gonna retire we were like ok the young hot shots have taken over...But forward to 2009 and Mark Martin racing for Hendrick Motorsports did we actually think that he would explode the way he did....NO! But i think it's time we call it a "Dream Season" for Mark if he doesn't win the championship, we won't be disappointed but we will all remember this season as how age really doesn't matter when it comes to racing it just matters all well you run...and if your going out there and beating the young ones then we know that there shouldn't be a certain age when it comes to thinking about retirement but it should be about can you go out there each week and stay with and run up there with all these new younger drivers.