It was probably about his 6000th episode — you can forgive the man a few duds.
I'll not forget that Paris Hilton interview: the one where he asked her what it was like going to jail and she twisted in her chair.
I will not forget Joaquin Phoenix being weird or John Key's Top 10.
But even Letterman accepts his was tired TV in a YouTube World. Everything about the set and the format felt a bit 90s, not to mention the interns trying desperately to gee up the crowd. "I can't HEAR you!"
Late-night TV is American comedy at its best. The Brits do wit, panel shows and subtlety. But the Americans own the night-in-night-out churn of highly formatted, tightly scripted, plug-my-book late-night laughs.
The Daily Show, The Colbert Report and the Late Show with Letterman might all be finishing at once, but perhaps unlike some other TV genres with less certain futures, comedy's on the up.
Stand-up is in the midst of a global renaissance.
America bid a legend farewell with Colbert, Fallon, Kimmel, O'Brien, Myer, Noah and Gordon all fighting for your belly laughs.
It's still a great time to own a TV.
• Jack Tame is on Newstalk ZB Saturdays, 9am-midday.