Question: If there is a fly in the room at your interview, should you try to catch it? If so, how long should you persist before you give up the good fight and try as hard as you can to focus?
Answer: The question is really if you can resist and also if this job is even the right fit. So the answer is persist. If your boss joins in and you egg each other on until one of you catches it, and then you do a fist pump in celebration, the job is worth taking.
True Story: I got the fly and got the job and now I love to eat lunch with my boss. Unexpected bonus: I haven’t seen a fly since, so that didn’t turn out to be an ongoing thing.