ploy suggests that the length of time a remedy has been used is
a measure of its effectiveness. Its promoters imply that if the
remedy didn't work, it wouldn't remain available. Some promoters
claim (sometimes truthfully, sometimes not) that their methods have
been handed down from generation to generation, are steeped in folk
wisdom, were derived from ancient writings, or the like. The falsity
of this ploy is easily seen by noting that astrology has survived
for thousands of years with no reliable evidence of any validity.
Note, too, that many genuine methods survive briefly because they
are replaced by more effective ones.