Plus, once you get to a certain point and believe you have the relevant facts, it's a pretty decent defamation defense to say you stopped there because you didn't believe you needed anymore?
(mind you, there's a fine line trying to prove the difference between that and intentionally not looking because you think there's a chance you will find something disproving, so I wouldn't go into things intending to find a cutoff specifically for defamation defense 🤷)