"Fully reusable" in all uses I've seen of with respect to aerospace it seems pretty fixed to me. We don't talk about "fully reusable" cars because there isn't an example of a non-reusable car. The "fully" part doesn't refer to how many times it lasts, just that the vehicle is reusable in whole instead of in part. "Wholly reusable" might have been a more semantically correct term, but "fully reusable" is what has stuck.