With people like that, I just start introducing my own margin-of-their-error into all communications. "Okay, he says it'll take two days, so I'm going to assume two to five and call after two" style lack of faith. Weirdly, they never seem to see my lack of faith as the justified act that it is. I view it as unfortunate micromanaging/double checking which I don't like to do, but they're often all "oh, you are so ORGANIZED". Buh.