How frequently does an industrial unit need to be calibrated?

Manufacturer recommended: Every 1000 -2000 tests or every 12 months (whichever comes first)

Australian Standards Requirement: Every 6 months

NOTE: 

Our factory setting presets calibration period to 180 days but it can be changed to 360 day however this has to be done by our technician.
If that period lapse, the unit will need calibration, regardless of the number of uses.