As Nicholas say it's process to completion so as long as your temperature is good, time shouldn't matter too much. If your temperature is way off though there are no guarantees. Kodak lists this step as having a range of 98.6-102.2, so it's not as sensitive as First Developer. If your having problems with the process most of the time it's the First Developer (range is only 99.9-100.9)- or your not mixing Color Developer properly (Part A & B etc..).