In this image released by CBS, David Letterman appears during a taping of his final "Late Show with David Letterman," Wednesday, May 20, 2015 at the Ed Sullivan Theater in New York. After 33 years in late night television, 6,028 broadcasts, nearly 20,000 total guest appearances, 16 Emmy Awards and more than 4,600 career Top Ten Lists, David Letterman is retiring. (Jeffrey R. Staab/CBS via AP)

David Letterman leaves late-night with thanks and a smile

When David Letterman signed off CBS’ “Late Show” for good Wednesday, he closed the book on more than his own incomparable career in late nig…