Like I told KV in an email. You invest all these years into this character. You get him to the top, you've gotten everything you could possibly want, he knows everybody and everything happening...Why would you want to quit using him?
I mean with my local group of runners I generally use him as a Fixer/Mr. J, but he sometimes can provide just the edge you need. My hope is that one day they'll be close to his level in experience and then he go back out doing massive runs against the Big Ten. I dunno, maybe I'm just a gangster GM and make most of my runs damn near impossible or something, but a starting character would never survive a run against a megacorp. I mean in second edition, it was different, I was all the time running against this corp or that corp, but that was during the corp wars if I remember right, but it seems like in 3rd edition the enemy has gotten tougher, but like I said, maybe I just made them that way.
Honestly my normal group ran the infamous Stuffer Shack run from the book First Run and would've wiped if I didn't have a nicely placed NPC walk in during the fight.