https://www.metv.com/stories/why-david-janssen-preferred-television

“The professional goes back to television, where the odds are better,” said the actor.

David Janssen said that he didn't know how to take time off from acting (https://www.metv.com/stories/david-janssen-said-that-he-didnt-know-how-to-take-time-off-from-acting)

"After a couple of weeks, I get restless.”