From Roger Kennedy's appearance on Booknotes in 1989:

"LAMB: Monitor Radio -- there's some in our audience, like me, who remember Monitor Radio. Whatever happened to that? Why didn't it survive?

KENNEDY: Because in a commercial system, the notion that you could talk about a story as long as the story merits simply is unacceptable. Some things are worth talking about for, my goodness, four minutes or even six.

LAMB: Or even an hour.

KENNEDY: Yes, miraculously. Well, it's crazy. How are you going to get the commercial bites in there?

LAMB: When did it die?

KENNEDY: We fell off that train. Gosh, I don't remember because the management changed and we all departed in about '58. It may have gone on after that.

LAMB: Oh, it did. I remember.

KENNEDY: We didn't feel it was exactly the same."