"I've met a lot of hardboiled eggs in my time, but you're twenty minutes"

This quote by Billy Wilder is a humorous way of stating that somebody is very persistent and tough to deal with. It implies that the individual is so difficult to handle that it would take twenty minutes to break a hardboiled egg, which is a metaphor for the person's hard personality. The quote is also a method of stating that the person has a great deal of experience handling difficult individuals, as they have met a lot of hardboiled eggs in their time. It is a funny method of revealing the idea that the person is really difficult to handle which it would take a lot of effort to get them to change their mind.