I was too young to experience TZ during its initial run and did not really begin watching them until seeing them in reruns in the 70's. And many of us, through the years are exposed to and have seen the various TZ episodes only through a variety of holiday marathons. Those marathons also have an expected list of wide spread favorite episodes, anticipated by fans that apparently must be and usually are always there like "The Monsters Are Due on Maple Street", "A Stop at Willoughby", "Eye of the Beholder", etc.
The lesser-known or less-cherished episodes are then more or less fed into and out of the rotation of each succeeding marathon, time permitting. We're certainly used to this with all season 4 one-hour episodes in particular, which end up getting very little play on the average because of time constraints. For example, before buying a book detailing all the Zone episodes decades ago, I did not even know there was a season with one hour episodes ! But all the shows within 30 minute format for the other four seasons should have been viewable from time to time over the years.
For me though, this one, "Young Man's Fancy" has slipped through the cracks. This is one I have so little familiarity with, recollection of and apparently viewed for the first time just a few years ago. While its not highly rated for the most part and I was not really crazy about it myself, finding an unseen original episode, out of the 156 produced is like finding a piece of gold in a familiar, but beloved pile of lead.