I'm only for keeping Teheran if they plan to shoot for .500 next year. In that case Julio will be helping a "winning" (or non tanking) team for 2017 and 2018, after which point you try to trade him for young assets.
And yes, I would always trade pitchers when they have 1-2 years of control. No, I would never extend one of them into their 30s by more than a year or 2. Maybe circumstances dictate they keep Julio for 2019, but if there is a replacement ready they should strongly consider trading him. Then they are in the position to say "we will only trade him for a great package, otherwise we keep him for another year". If they are always in that position they should be able to parlay that into good talent constantly.
Problem with Julio is he will not sign an extension. He will hit the FA market after his age 29 season and sign a huge 5+ year deal that takes him well into his decline. The Braves should look to lock up pitchers that prove themselves early to contracts with options at the end just like they did Julio. Wisler is not a candidate for such an extension, but I think Folty will be.
