Because they are forced to squeeze so much of their humour from certain limited character traits and situations, sitcoms tend to get boring relatively quickly. The creators of the best of them realise this. The Office (UK), Extras and Fawlty Towers, three of television's greatest comedic achievements, featured just 12 episodes each, over two seasons. The formerly-great The Simpsons, by contrast, has now been going for more than 600.
The Good Place is into its early 20s, episode-wise, with just one episode left in its second season, and it's not likely Netflix will allow its creator, Michael Schur, to walk away after that, even if he wants to, which he shouldn't.
It's hard to write about The Good Place in a way that is specific enough to be informative while not revealing key plot points that would destroy the viewing experience for anyone who hasn't yet seen them. All you can really say, without having to preface your article with "spoiler alert" is that it's based on the experiences in the afterlife of its four central characters, plus another character played by Ted Danson.
But what Schur and his team have already achieved in the first two seasons is to create something that is so continuously fresh and innovative that it feels like it's just getting started - and knowing modern commercial realities, it is.
The second season features all the same characters, but after a dramatic season one turning point it has become a completely different show. That is an act of creative bravery in a commercial world focused so heavily on brand loyalty - asking viewers who had invested in one set of beliefs to invest in a whole new set.
Schur had to ask himself whether viewers would relate to the concept of the second season as well as they had to the first, which had been a critical success and at least enough of a commercial success for a second season. (Netflix doesn't release viewer numbers so we can never be sure how commercially successful any of their shows are.)
This act is just one of many brave things about the show, including the fact that its characters spend a surprising amount of time having actual classroom lessons in moral philosophy, which are things that even professional philosophers would define as "not really entertainment".
More or less a whole episode in season two, for instance, is devoted to "The Trolley Problem", typically the basis of lecture one in Moral Philosophy 101. Watching it, you can almost hear philosophy professors around the world embedding the video in their PowerPoint presentations.
Philosophy professors and self-help authors have long understood that "What does it mean to live a good life?" is the most important question humans can ask themselves. Generally we use TV as a way to avoid asking it, so it's an act of severe subversiveness to get us asking and watching simultaneously.
It's a great achievement and a great show. It can't last forever, but what ever does?
Oh, yes. The Simpsons.