When it becomes clear the writers don’t have a long term plan. I’ve been rewatching Once Upon A Time. Still my all time favourite show but I’m confident that the writers only had a clear plan up to the end of season 3, after that things start to get fuzzy. Storylines get abandoned and unresolved, things happen that seem to be setting up something that doesn’t come, storylines happen that almost contradict past events (for example Snow and Charming having a dark secret about what they did to Maleficent, when you watch prior seasons with that in mind, it’s really weird nobody brought it up sooner). Yeah, you can just tell they didn’t plan past a certain point and they started adding lore that didn’t add up

Sometimes you realize that the main story arc keeps finding new reasons to continue, after lots of surprise twists and turns that each give another episode. Like they finally find their killer, after a whole bunch of running around, escapes, shoot-outs, stunts, explosions, etc. but it turns out he’s been working for someone else all along, and now we have to find the Boss. It will never end, and all the plot manipulation doesn’t serve a better story, it just keeps us watching so we can consume advertising.

My son is always complaining that a lot of these series probably started out as a movie, but Netflix, et al, want constant “engagement,” so if you want Netflix to stream your content, you better stretch it into 10 episodes, with a cliffhanger. Quality isn’t important, just engagement, so a good movie concept gets beaten to death as a series.

That’s why a lot of British shows are so good. They’ll say right up front that this entire series is only going to be one season of 3-6 episodes, and that’s it. They take as much time as they need to tell the story, then quit. They don’t just keep screenplay masturbating.

Walking back character development/growth.

When they have a contained shark that the main character decides to jump to keep establishing his cool.

Seriously though, when threat of the week escalates to such a degree that it becomes a potential universe calamity, it’s hard to be worried about Murderer McGee stabbing 13 people to death.

Shoehorning in a new main character

Shoehorning in a new main character to try to increase appeal

Shoehorning in a new main character to try to increase appeal to sell more merchandise

Shoehorning in a new main character to try to increase appeal to sell more merchandise because the higher ups made a decision to drastically change the original main character in an obvious cash grab

I’m looking at you, ya pop tart colored unicorn

The actors and writers get bored and do a musical episode.

Identical twins…trapped in the basement…winning the lottery…tonight, on a very special…cousin oliver

When it’s based on a book/series and outruns the source material

When the main character(s) have a baby. When that happens it’s time to go.

It’s the pilot of a sitcom in which a goofy husband and hard nosed wife blah blah zzzzzzzzzz……

Joss Whedon is the executive producer.

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Changes in over or undertones. IE change in overtone being it suddenly turns into an action comedy when it was a gritty murder mystery. A change in undertone would be like if two characters that never had any romantic tension, or were canonically confirmed to not have romantic feelings for each other, suddenly were cofessing their feelings for each other.

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When the potential long-term impact of the events keeps increasing, but the actual long-term impact keeps decreasing.