Just to offer an alternative position, I'd say that spoilers can only exist for stories (be they films, television episodes, novels, etc) that have not yet been released
. Spoilers used to be a word referring to plot details that were known before the release of the material. Now it has been expanded to refer to any
details of the story (including non-plot-relevant details) that someone else
hasn't learned about yet!
There will always
be a segment of the fanbase that hasn't read a novel or seen an episode. Therefore, by the current definition of "spoiler", there will always
be spoilers! That's ridiculous, though. If a spoiler is anything that someone hasn't experienced yet, then all of Shakespeare's works should be spoiler coded when discussed, and in fact every story that exists in human culture
can't be discussed without spoiler codes.
The idea that "spoilers" can exist for stories that have been out and available for any
length of time strikes me as ridiculous. That not everyone will get to the story immediately is no one's fault, it's just a fact. Walking around on eggshells, trying to not "spoil" plot details of a released story for people who have not yet read it is pointless.
In summary, I think we should return to a definition that only categorizes plot details of stories that have not yet been released
as spoilers. Anything else is just silly.