If you have multiple users wearing the same headset, you should run eye tracking calibration each time the headset changes user. Eye tracking calibration guides the user to adjust the IPD (interpupillary distance) to make their face, as well as the vertical fitment on the head. This calibrates the eye tracking to send the most accurate data possible back to the Omnicept sensors.
If you want your application to have the most accurate eye tracking, then you could recommend your users running eye tracking calibration everytime they put on the headset but we do not believe this will be the norm.
To learn how to integrate eye tracking calibration into your own application, please see our guide to calling eye tracking calibration from within your application.