I know it really isn't dangerous but I'd be really sad if I had to dose Corid constantly.
I don't know this for a fact but I would be concerned about nutrition when dosing a thiamine blocker for such a long portion of my birds' lives.
Not really an effective one.
Given the right conditions, coccidia can survive up to 18 months in soil. They don't survive long below freezing or above 130F. They also can't survive in completely dry soil.
Even if you baked or froze your soil, they would return. They are spread on people's shoes...