Supernatural would outlive us all, I've spent a not insignificant amount of time over the last few years considering what the legacy of the show might have been had it ended after Season 5, with the culmination of the original angels-and-demons arc planned by series creator Eric Kripke.
As it stands now, with 15 seasons of the family business under its belt, Supernatural is the longest-running sci-fi or genre series in American broadcast TV history (Doctor Who is the longest-running sci-fi series in TV history).
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