Odds of Hanging On
Once you're established, your odds of hanging on are pretty good. This is one career path where advanced age doesn't really get held against you.
In fact, the older you are, the more you might be seen as a respectable voice on whatever sport it is you're blabbering on about. The viewing audience gets used to seeing your face and hearing your voice, and a sports media company isn't going to boot you if the viewers feel comforted every time you appear on screen.
Avoid scandal and keep your reports engaging and lively, and you should be able to cast your sports for many years to come.