Evaluating measurement uncertainty frequency

You asked :

"I would like to ask is there guideline on the frequency to evaluate the measurement of uncertainty ?

Measurement uncertainty (MU) is a once off activity once method development is finished. When Method validation is planned, you plan your approach to evaluating measurement of uncertainty. Depending on the method, your method validation data and longer term precision is used for evaluating  /  calculating  MU.

You also asked

Under what circumstances that the measurement uncertainty have to be re-evaluated?"

If any method conditions change then a method must be validated or verified again and MU must be re-evaluated as the sources of uncertainty may have changed.

Have a look at my reply at https://community.advisera.com/topic/uncertainty-measurement/ for further information and resource links.