The storyline's success wasn’t thanks to Dallas's quality, or America's fondness for star Larry Hagman, who’d turned a secondary character into the archetypal man-you-love-to-hate, and the breakout star of the show. The third season finale "A House Divided" aired on March 21, 1980, and Dallas didn't return to screens until November. Over that summer, Ted Turner's fledging Cable News Network launched, and embarked on the then-daunting concept of reporting the news 24 hours a day—with feverish speculation over J.R.'s assailant becoming a popular and frequent topic.

As with many classic TV cliffhangers, the show's writers went into things with no particular idea of how to resolve the mystery, arriving at the conclusion just by a logical process of elimination. Another example of that loose approach is "The Best of Both Worlds," the third-season finale of Star Trek: The Next Generation, which ended with Captain Picard captured by the alien Borg and transformed into a cyborg zombie. The writer and showrunner Michael Piller later admitted he had no concept of how the next episode, which led off the fourth season, would resolve the cliffhanger—he just knew the show needed something to keep audiences on the hook over the summer. The Next Generation was a steady cult hit before the episode, but its ratings jumped by 25 percent between seasons, and the show graduated to mainstream success.

This isn’t to argue that cliffhangers belong to some bygone age of television writing. But the traditional September-to-May scheduling of the glory days of network TV certainly does, and with its decline comes adjustments. The summer is no longer a period of dead air around which buzz for the fall schedule can build. The TV landscape is constantly littered with new entrants, emerging mini-networks, and strangest of all, old shows being sold into syndication for streaming services—now, a whole new generation can be surprised by Picard's capture while watching on Netflix, except there's no need to wait three months for the conclusion.

AMC's Breaking Bad was a show that harkened back to the glory days of edge-of-your-seat mysteries, ending every season with a bombshell shot (a plane exploding in the sky, Jesse Pinkman pointing his gun at the camera) and many tantalizing dangling plot threads. But the show didn't find ratings success until it popped up on Netflix; its highest-rated episode by far was the series finale, which drew 10 times the viewership of any other season finale the show aired. Audiences could now wait for almost the entire show to be ready for binging before watching the final episodes live. America's patience for long TV layovers, it seems, has significantly waned.

This is, perhaps, where the increased debate over "spoilers" has come from. In 1980, if you wanted to know who shot J.R., there was only one way to find out: tuning into CBS on Friday at 10 p.m. Now, a push notification on your phone can tell you what happened on The Jinx right after HBO airs the episode, and fans will complain about years-old plotlines being ruined in articles online because they haven't gotten around to binge-watching that particular show yet. The pop-culture website The A.V. Club continues to publish two different reviews of Game of Thrones every week—one for fans who've read the books they're based on, and one for "newbies," just to avoid plot revelations being discussed in their respective comment threads.