Nothing upsets a reader as much as a book that doesn't end on the last page.
Nothing upsets a viewer as much as a motion-picture that is abruptly cut off before the story ends properly.
If an episode of COLUMBO stopped before Lt. Columbo had solved the case, I would be upset.
But... have you ever wondered? Why do we expect a story to neatly fit into the limits of
A) the 200-500 pages of a single book
B) the 50-60 minute duration of a single TV-show episode
C) a 90-120 minute movie?
D) a stageplay lasting 1-4 hours?
(No offense to Lt. Columbo, but how does he ALWAYS manage to solve a case in 3-5 days? Many murder cases take months, years, even decades to crack.)
Real life won't fit into a 90-minute movie.
The practical explanation is that most media - such as print, movies on film rolls and television - impose strict boundaries on the story's length. The full complexity of life is simplified and abridged for the sake of the medium. (Again with the McLuhan reference!)
You won't find single 10,000-page novels in the bookshop, because the publishing industry can't physically print, edit and distribute a book that's 1 meter thick and weighs 10 kilos. If you wanted to tell a story which required that length, you'd have to break it up into several volumes - and even that wouldn't be without its problems.
Also, the reader's patience and stamina impose limits to story length. If you've ever sat through a "Director's Cut" movie, and had to go to the bathroom during the middle of the film, you know what I mean.
And of course, the author's patience with a single story isn't limitless either.
In practical terms for the individual writer, you may have run into the Limit Problem when you try to cram too much plot into a 100,000-word novel. (I have!) Consider breaking up your plot into individual novels. You don't like doing so? Well, what can you do? Even J.R.R. Tolkien had to see his first U.S. printing of THE LORD OF THE RINGS broken up into three books.
Digital technology now makes it possible to make stories - novels, motion pictures, comic-strips (see Scott McCloud's "Carl") of greatly extended length and complexity.
You could - if you were ambitious or mad enough - post an incomplete book online, and just keep adding to its length for the rest of your life... until, with your very last breath, you completed it with the ending.
("Behold: The World's Longest Novel! Bigger than The Bible! Longer than War And Peace! Lengthier than *GAAGHH*....")
Or, if you were utterly insane, you could digitally cut-and-paste together every single episode of the TV soap DALLAS into a single, gigantic movie ("DALLAS - THE COMPLETE SAGA") and post it online. Behold, the world's longest film!
Then again... most writers barely muster a single 100,000-word novel. So why should they worry about the Limit Problem?
One worry is Posterity. Many of the ancient classics of literature are probably surviving fragments of even bigger epics. THE ILIAD and THE ODYSSEY seem to end abruptly, but we can't say for sure the Greeks ended the story of Odysseys when he returned to Ithaca.
Perhaps the Internet will give birth to Never Ending Stories... movies and books that get extended endlessly, over entire generations.
And here this blogpost runs into a Limit Problem of its own... so I should stop here.