Spoiler alert! Probably not.
Personally, I believe in a statute of limitations, whereby you no longer have to feel responsible for not spoiling things after they've been around long enough, but you still shouldn't do it on purpose like a jerk. Of course, what exactly even constitutes a spoiler is different for different people, so maybe the Internet prophylactic method suggested by Emily Eifler would be a better way to go. PBS Idea Channel tried to find some other solutions. Get working on the spoiler condom, science.