Hubby says that Star Trek: Enterprise series (season 4) goes bad after the Mirror Darkly episodes. We'll stop watching at that point.
Knowing when to stop is quite a skill.
Hubby left Hammer Into Anvil to the end when we watched The Prisoner and missed the actual double final episode; and it was a great finale.
We stop the third Lord Of The Rings movie when Aragorn says that Hobbits bow to no one. I'd love to chop the dvd so it stops there by itself. The whole return to the shire ending is nothing like the book and hence a waste of time.
The Matrix trilogy can be vastly improved by only watching the first movie.
The same goes for Star Wars. We like Star Wars, The Empire Strikes Back and will tolerate Return of the Jedi for the space battle and Luke/Vader scenes. Episodes 1-3 are kiddy cartoons and not really of interest.