I've been thinking about it, and I feel that the initial cancellation of Star Trek was what saved it. Say, Star Trek was never moved to the Friday death slot (Friday at 10pm), and was in fact moved to Monday at 7pm where it would be in the best place for its core audience. In addition, it would have also been given proper funding. It would have probably initially lasted 5 seasons from 67-72. Something tells me, however, that given the limitations of special effects technology at the time, and given the gradual decline in quality that was presumably unrelated to time-slot, I feel that after 5 seasons they would have slowly run out of original stories, interest in the show would have slowly plummeted, and it would have simply died with a 2-hour finale. Since the series did end prematurely, it left the world wanting more. "Where did Kirk go? Spock? They aren't done with their mission!" I also think the nature of the show by the 5th season would have changed considerably. I think it would have involved more music, more hot lady aliens, more helpless damsels in distress, more romance, more fight scenes, and it would have taken away from the substance of the show. It probably would have been commercialized to hell. If it didn't have that 10-year pause before the first movie, and Battlestar Galactica in 1978 to incite interest in Sci-Fi, I don't think Star Trek could have become what it has become today. Or they would have started Star Trek: Phase II in 1972-73 and it would have been amazing. All speculation.