Since announcing two weeks ago that he was leaving, the 42-year-old Kilborn has had difficulty explaining why he is walking away from a show that has seen its audience grow by more than a third during his tenure.
He has said it was simply time to do something else and returned to that theme Friday.
"It's one of the happiest days of my life, and I'll tell you why," he said. "I got to do a dream job ... My job is done here. It's time for me to move on. I dreamed of early retirement and that's probably what I got."
Kilborn had drawn solid ratings for CBS since he took the time slot over from Tom Snyder. Since 1999, the audience for the hour that follows the "Late Show with David Letterman" (search) had grown 34 percent to this season's average of 1.7 million viewers.
Some of Kilborn's favorite guests returned to say goodbye, including actors Vince Vaughn, Marlee Matlin, Martin Mull, Adam West and comedian Will Ferrell (search). Wayne Newton sent his regards via satellite from Las Vegas.
"I'm going to miss you," Kilborn said. "Maybe I'll see you down the road."
Kilborn was the original host of Comedy Central's "Daily Show" (search) and had a role in the 2003 film "Old School."