AD7367 ADC calibration

I am using the AD7367 and am interested in achieving better accuracy.  I am using a high accuracy external reference.  I am using the ADC in either the +/-10V or +/-5V range.

Can I perform a one time gain and offset calibration, or would I need to do that calibration on every startup to get a performance advantage?  Is there a recommended procedure for performing the offset/gain calibration of this part?