The pet rock lasted about 6 months, albeit over 1.5 million pet rock sold.
The Chuck Taylor All Star sneaker from Converse has been a fad since the 1930’s and continues to steamroll in sales 80 plus years later.
The typewriter had a good run since the 1860’s, but I doubt you care to own one any more (unless you are a collector… and that does not count as a fad).
From cabbage patch kids to the wheel, everything is ultimately a fad. The question is just how long the fad will last. One day? One month? A year, decade or century? Perhaps eternity (water seems to be doing well in this classification).
How long will the next fad last? Your guess is as good as mine.