Once completed as many times as the director feels comfortable, the tech will end. Any number of actions can usually be taken after a tech such as the running of problematic scenes or acts, another dry tech to work out problematic technical issues, or certain performers may be held to work with certain effects for which the other performers are not needed.
After completing the technical session as many times as the director feels comfortable, the tech will end.  This allows for various actions after a technical session, such as running problematic scenes or acts, another dry run to address technical issues, or certain performers may be required to work with specific effects that other performers are not needed for.