Well, I can’t speak for the American market, but the BBC wanted copies destroyed or returned when the contract was up. I suspect that some US stations might have kept the contract going for years so they may have kept a copy that they might air periodically. But one a contract was up and not renewed, the tapes went back or got wiped. With the BBC’s bad archiving, lots of things got lost because of this. The occasional stray turns up that didn’t get destroyed or returned so the policy is well documented in hopes more strays turn up.

So my guess is that tapes sent out for broadcast were wiped afterward.