I recently answered this question:
Several of the other answers have details which might be considered spoilers (they give away plot details). However, they're spoilers for a movie that's been out for 2 years.
Do we have any sort of guideline for spoilers, specifically in terms of "age" of the content?
I could understand not bothering with spoiler tags if you're going to mention that Darth Vader is Luke's father, but discussing things from a movie that's 2 years old seems like it may be spoilers for some people. Of course, as the question ages, the "age" of the movie relative to the point in time at which the question is being read will change. Should ALL spoilers be tagged as such?