Columbo* was known for saying "just one more thing."
We seem to have adopted "before I let you go" as a go-to way of asking one last question.
A tip from a "Memmo" reader led to a search today of NPR archives. The phrase "before I let you go" produced 820 results; 90 were heard in just the past year.
Broken down by show, All Things Considered is far ahead: 284 results. Morning Edition had only promised freedom 107 times.