This question cannot be answered unambiguously. Decisive are the application of the flowmeter, the frequency with which the flowmeter is used and the specific properties of the instrument.
We recommend determining the calibration period per measuring instrument individually. Usually the calibration applies for the duration of one year. However, if highly accurate measurements are needed, the measurement uncertainty may be covered for a shorter term (e.g. 90 days).
After a number of calibrations, the course of the measurement deviation is usually easy to estimate. You can then decide to extend the term (for example 1 year, 2 years or 3 years). However, this method is not a guarantee.