Jason Snell on how the TiVo Season Pass list makes him feel like a TV executive (The Incomparable episode 152, around 24:30):
Because you can cancel shows yourself — so, The Office, they had that episode where Jim and Pam got married, and I said, “What a lovely season finale this is.” And my wife said, “No, no, they’re still going to make episodes.” And I said, “No, what a lovely season finale this is.” And I canceled the show, and I moved on. Apparently there was a big hubbub about how there was a final episode of The Office this spring. But the final episode of The Office aired in my house — as far as I’m concerned — three years ago, four years ago. It was very nice, and then that was the end.
I strongly endorse this attitude. The metaphor I use is poorly written fanfic. If a series has lingered beyond the point of negative returns, I imagine that those ongoing episodes or movies or books are just non-canonical fanfic written by someone else. This trick helps protect my affection for the parts I loved.
The Office is a great example. My version of the show also ended with that wedding episode, more or less. I came back for the delivery of their baby, half a season later, and consider it a denouement to the series. But even that is being generous, since my wife was pregnant when the episode first aired. The remaining three and a half seasons are all fanfic to me.
Canonical is in the eye of the beholder.