How many nodes do you need in your neural net in order to account for the variation of human behavior, the influence of happenstance, etc? When your model fail

How many nodes do you need in your neural net in order to account for the variation of human behavior, the influence of happenstance, etc? When your model fails to converge, do you tell your government customer that you can't actually produce a score and give back the $200 million or whatever you got for the contract to create such a score?