How long does it usually take to do a OPAT test?

All of the OPAT tests have to be given on the same day. People are allowed up to five minutes to calm down between events.
https://tanukisunset.io/

All OPAT events must be administered on the same day. Individuals are authorized to take up to five minutes to recover between events, but may elect to proceed when ready. All four events must be completed within one hour. The test period is defined as the period of time that elapses from the start to the finish of the four events (from the first trial on the Standing Long Jump to the last shuttle of the Interval Aerobic Run).

The whole thing can be completed easily within an hour to an hour and a half. Its only a few events.