The potency of Botox (and other brands of botulinum toxin) varies by as much as 30% from lot to lot, so considerable variation in the perceived duration of action, which is related to the potency, is not at all surprising.
This is a separate matter from the question I was debating with JL, which is whether JNJ’s PurTox has a longer duration than Botox on average.
“The efficient-market hypothesis may be
the foremost piece of B.S. ever promulgated
in any area of human knowledge!”