Does it seem to anybody else that this page might benefit from a short list of counter examples, ie: American Long-runners
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Last Of The Summer Wine is listed as averting this trope, but since it has only had 289 episodes over 28 series, it's averaging <11 episodes per series. Which fits squarely in this trope (there may be specific series which avert it, but not the entirety of the show).
"Some American shows that start off weak can grow their beard when the show would have long been over in the UK."
That's interesting, since here in the UK we take the same view of US television: ie we think that US networks are overly-competitive and will axe a show mid-season without giving it a chance to "bed in" whilst many British shows which "failed" on their first season (or "series" as we usually say over here) are often given a second chance and go on to become huge successes. This is what famously happened with "Blackadder" but also applies to "Men Behaving Badly" and other shows.
I'm not sure if this should go on the page or not, but I have made an observation with regards to season length:
Long seasons tend to cause "viewer fatigue" due to constantly having to remember that there's a new episode of the show on if you want to keep up to date with it. The usual UK upper limit of 13 episodes seems about right, given that after three months of trying to remember to see something weekly, you're rather worn out and you both feel a sense of accomplishment for making it through the season, and welcome the break that you're now going to get.
Accidental mistakes are forgivable, intentional ones are not.