I actually agree with this Atrios snidety as a standard.
There's not a good reason to keep people like David Broder and the recently retired Bob Novak on newspaper payrolls past a certain age - or at least a proven reason. I know that there's some sort of theory that they've built contacts and history and wisdom that the newspaper can tap into with the columns, but frankly, they've also built up a premium cost and predictable processes and an established coterie of quote contacts and a predisposed viewpoint of the world that has gotten more than their share of time, and it's time for them to go. The same argument newspapers make about columnists can be made about state government employees and I don't see much clamor to keep the state government employees around past mandatory retirement.
These aged scribes have an audience they can tap into with their own blogs if they're really that damn interesting, and so they should go do it. I suspect that David Broder doesn't want to learn how to do a blog, and that's really the problem - if a columnist doesn't want to learn on the job, then what good are they?
I'm not for doing this on the basis of age, however. Years of total columnist service should be the standard - so many years and you're out. You know - term limits.