Most often, all that's required is the ability to demonstrate the instrument is within current calibration.

There are instances though where the period between calibration can be extended based on the results of previous cal. (Not usual with electronics that may tend to drift, but common enough with some aspects of metrology).
You'd need to retain sufficient records to enable you to continue to justify that change of cal. period.

No statutory requirement I'm aware of unless calibration is a safety-critical matter - e.g. gas monitors - in which case 3 years is the norm.