Supernatural is an urban fantasy series about Sam and Dean Winchester, two brothers who hunt monsters. The show started off with the duo fighting the likes of ghosts, werewolves, and vampires, but quickly escalated to include demons, Death himself, and even God. The show usually sticks to a monster of the week format, with occasional episodes that deal with that seasons' over arching plot. Supernatural will be wrapping up soon after fifteen years on TV, but it was only supposed to run for five. Original showrunner, Eric Kripke even stated that he only planned to helm the show for that long (which is what happened). It would be easy to dismiss the later seasons of the show. At times it felt like the Winchester brothers were in something of a holding pattern, and Chuck as a character certainly took a turn at the end of Season 14, but there is still plenty to love in the years Supernatural went beyond its original plan.
Perhaps the part of the show which benefitted most from going past its sell-by date were show's extended cast of characters. Castiel went from being a recurring part of the show to being one of the main three characters. If any proof was needed that the angel's importance had grown to similar levels as the Winchesters themselves, it was Misha Collins standing alongside Jensen Ackles and Jared Padalecki for the announcement that Supernatural was coming to a close. Crossroads Demon, Crowley also benefited from greater attention thanks to more episodes. Thanks to the events of Season 5 the character got to take the throne of hell, and the following years of the show showed how he ran things now he was in charge. Chuck even showed up again, confirming in Season 11 that he had been God all along after fans had been suspecting even since it was hinted in Season 5's finale. Supernatural also got more mileage out of relatively smaller characters, like Samuel, the Winchester's grandfather, or their brother Adam. Fans even got to see more of Gabriel long after he was believed to be killed off for good. Seasons six to ten showed that there was so much more that could be done with the characters, and that potential did not go wasted.
It's not just returning characters who got to shine either. There were some real fan favorites who made their debut in Supernatural in the last ten years. Charlie was a fun, tech-savvy lesbian who got to go to the land of Oz with Dorothy (yes, that Dorothy), and contributed a lot to the show's more comedic side. She was such a hit that fans were outraged when she was killed off by the villainous Styne family. Similarly, Crowley's mother Rowena became a staple of the show, and had a great character arc. She started off as a villainous witch, but grew to be a badass witch instead, changing so much that when Sam killed her in the show's final season, it was on her orders for a heroic sacrifice instead of just another bad guy. Though on a side note, Supernatural should probably have stopped killing off so many members of its cast. These characters, and others made their mark on the show just as much, if not more than the cast they replaced from the show's infancy, and provided something of a fresh dynamic with the main characters for the show to work with. They were a sign that Supernatural still had fresh stories to tell, and new faces to make up for all the old favorites who had been lost along the way.
Jared Padalecki once said that they had been told by the higher ups at the CW that as long as the ratings held, Supernatural would continue for as long as Jensen Ackles and he were willing to keep going. The show had a certain sense of security to it, and everyone involved with making it had a lot of fun with that. Meta episodes had been a part of Supernatural ever since Winchester brothers found out that a guy named Chuck was making books based on their life, and later episodes ran with it. In one episode, Sam and Dean are transported to a universe in which their lives were just a TV show. In another episode they had to save high school students who were putting on a play about them, and yes it was a musical. It didn't stop with meta episodes either. Previously killed off characters came back via time travel. Dean got to kill Hitler (and he loves to talk about it). There was even a crossover with Scooby-Doo. Dean, Sam, and Castiel were sucked into the television for a fully animated adventure with the Mystery Inc. gang, and it was awesome. There was so much creative energy on display, and it all came from the makers of the show feeling secure enough to just go with whatever fun, or weird ideas they had at the time.
Not everything should keep going on and going. Sometimes it's better for a TV show or movie to bow out while the going is still good. Supernatural on the other hand, embraced the opportunities provided by its later years to tell new and interesting stories, with equally new and interesting characters. Whole other universes, a secret society called The Men of Letters (think Hunters with better funding), and even God's sister Amara, were signs that Supernatural had plenty to offer beyond Season 5. Not only will Supernatural end as a richer, more complete version if itself than if it had bowed out ten years ago, it will do so with the knowledge that the people making it truly got to make the show they wanted to make. In a world where plenty of shows are cancelled before their time, or have to make do with a one off special to tie up loose ends, isn't a show that truly got to end on its own terms something to celebrate?