There's seemingly no end in sight for The CW's longest-running series "Supernatural" and for good reason. The cast and crew are happy to keep making new episodes and the fanbase is as hungry as ever for the continuing story of Sam (Jared Padalecki) and Dean (Jensen Ackles) Winchester, along with their angel ally Castiel (Misha Collins). Surely the show has to end one day though, right? After all, nothing lasts forever -- especially on TV. While "Supernatural" will no doubt go out in a blaze of glory, it's Collins who has an idea of when it could feasibly happen. "I think the number should be 666 [episodes]," he says on the show's Vancouver set. "Six hundred and sixty six?" Ackles asks incredulously. Padalecki adds, "That's in like 18 years." RELATED: ‘Supernatural’ finally addresses the psychic elephant in the room His math isn't wrong. To reach 666 episodes -- under the show's current annual order of 23 episodes per season -- "Supernatural" would have to go all the way until Season 30. Of course, that's not exactly impossible. After all, "The Simpsons" was just renewed until Season 30 and there's still plenty of road for "Supernatural" to travel. "I think as long as there's still story to tell, which ... I think one of the great aspects of the show is that we're not necessarily bound by reality," Ackles says. "The stories are, you know, it's kind of limitless. And I think that as long as there's still they're still staying true to the show and the characters are still being written in a way that we still get inspired to play them, then I don't know that there is a number necessarily." With that in mind, the stars of the series, currently in its 12th season, are taking things as they come. "It used to be just one step at a time," Padalecki says. "Now we're like just one, one and a half season stretch at a time. 45 more episodes at a time." In fact, the cast and crew recently crossed the 250 episode milestone with very little fanfare. RELATED: Crowley & Castiel are the ‘Supernatural’ buddy cop duo you’ve been waiting for "I think we wrapped at 8 o'clock, I think it was a Friday even and I was like 'I'm gonna grab a beer and hang out in Ackles' trailer and have a beer or something,'" he remembers. "I'm like 'is Ackles ...' [and they're like] 'yeah, he's already cleaned up' [and] I'm like 'cool'. So I kind of clean up and I'm like 'Hey, Jensen, can't find you. Are you in your trailer, did you go back on stage? Are you in the camera truck or something?' He's like 'I'm almost home'. I was like 'alright, guess it's really not that special.'" Don't expect the end of the show to sneak up on fans, though. Padalecki says, "I like to think that there will be warning and there will be a group decision." And as for what happens once the show is over, the actor himself isn't so sure. "I don't even know what life would be like," he says. RELATED: Don’t stop believing: ‘Supernatural’s’ 12-year crisis of faith "Supernatural" airs Thursdays at 9 p.m. ET/PT on The CW.