A recent conversation with co-workers about NASCAR sparked this question: At what age should a driver retire?

I think it's obvious it would be different for each driver, based on how successful he is, and other factors.

It's not like in baseball, basketball, football or ice hockey, sports in which players know their careers will most likely end in their 30s, or sooner.

Every once in a while a player comes along who is exceptionally good and stays in the sport beyond what's expected of him, and it works.

In NASCAR, some drivers have raced into their 60s, and it doesn't work.

Most retire from racing in their late 40s or early 50s.

Personally, I think there are a few guys racing now who need to move on.

One driver who stayed in the race car way too long is Darrell Waltrip.

If it weren't for provisional starts, Darrell would not have qualified for a lot of the races the last year he was in NASCAR.

He couldn't qualify on his own and, being a past champion, NASCAR allowed him to use a past champions' provisions to get in the race.

I'm pretty sure it was the following year NASCAR changed the provisional rule so past champions could only use it three times in a season.

The King, Richard Petty, raced a little longer than he should have, too.

Yet he retired from racing the right way. He let the fans know at the end of the 1991 season he would be hanging up his helmet at the end of 1992.

Richard's last year was called the "Fan Appreciation Tour" because his fans have and will always come first.

I give a lot of credit to drivers Harry Gant, Rusty Wallace and Cale Yarborough -- to name a few -- who had enough sense to stop racing when they were still competitive but getting up in age.

I also give credit to Michael Waltrip for realizing he would be better as an owner instead of a full-time driver.

So, I guess there's no particular age a driver should retire. But it would benefit NASCAR and the fans if drivers were to hang up their helmets when they've passed the height of their career and are no longer competitive.

The Sprint Cup guys are in Sonoma on Sunday at 3 p.m. on TNT.