Lol wat. Wacha's only turning 27 this summer. He's pitched 650 MLB innings, dude; 108 MiLB IP sprinkled in among those. That is in no way, shape, or form "a fair bit of mileage". There's a really good chance he hasn't even hit his prime yet.
While I would never tell someone how to run their team, I feel like you're overvaluing prospects and will be mired in a perpetual rebuild if you don't hang on to good MLB talent. Even though players are beginning to hit their peak at a younger age, most prospects still bust. I understand why you made this deal, though. In a vacuum, it's a decent return for Wacha, in my opinion. Sanchez is an interesting prospect, but if he busts, you didn't exactly get much in return.
Meh, I dunno. Play on.