Wow, I did not see that one coming!
I started watching in 2008. I remember catching Mystery Spot (Season 3, Episode 11) when it originally aired. Every time Sammy woke up to Heat of the Moment playing on the radio, I couldn't stop myself from laughing ("Rise and shine, Sammy!").
Right there and then I was immediately hooked. I went out, bought the DVDs, and started from the beginning.
Whatever the reason is behind concluding Supernatural, I'm thankful for all the years of entertainment the cast and crew has given us. It was one hell of a ride.