One problem with that is it could be a loooong time before (pretty much any) of those types of broadcasters actually set up a re-run of a show already
broadcast. Discovery Channel sells tapes of their shows too...If I don't happen to catch it when it's running, it seems to take forever before they
re-run it.
...Of course, that gives more time for the more "impatient" people to order the tapes...