I discovered the animated series during its initial run on NBC, but I have caught it in syndication at various times in later years.
In Australia, we got TAS first-run on Saturday mornings in glorious b/w, then several repeats "in full colour" when weekday breakfast TV really took off in the late 70s. For a long time, "Mr. Spock's Time Trek" from View-Master (21 "Yesteryear" images in 3D) was my only tangible proof that the animateds existed. Bjo Trimble's "ST Concordance" entries were highly valued.
Western Australia got another run when video recorders had become common, and so a few people in Perth staved off our rememberings back east with grainy crosstapes of crosstapes of crosstapes.
Then, TAS even came back to Saturday mornings in the 90s, when TNG was at its height of popularity, probably just after the dust had settled on rights ownership after the Filmation closure in 1989.