How Many Weeks Should Pass Before a Person Contributes at Nearly Full Speed?

The most dangerous ones are the poor cultural fit and the high performers. If you've hired the right person for a significant role, how many weeks should pass before that person is contributing at nearly full speed? I have had so much fun with this question only when I ask it of multiple partners and I make them answer in weeks on a slip of paper. It relates to your expectations in hiring and managing people and how patient you are.