Nyhan wants them:
When will Gail Collins come up with some new material? Her end-of-year quiz includes her 12th Bristol Palin reference since October 2008, her 13th reference to Mitt Romney putting his dog on the roof of his car since August 2007, and fourth joke about John Boehner crying in the last month. She only became a columnist in July 2007 and she's already recycling material. Even by the low standards of op-ed columnists, it's been an incredibly fast decline toward intellectual and creative exhaustion.
But term limits only make sense when there are a limited number of spots, and someone's longevity is preventing someone else getting a point across. That was true a decade ago; it couldn't be less true today. The institutional sinecures keep disappearing. Eventually, only Richard Cohen will be left.