Master instructor certification is valid for 2 years. To re-certify, you must attend the Master Instructor School in its entirety. The Master Instructor School is usually offered twice a year.
Instructor certification is valid for 2 years from the date certified. After that date, you are not to conduct user certifications or courses of any type.
User certification is valid for a calendar year from the date of the class.
For example, if a user certified March 11, 2017, they would need to re-certify sometime in 2018, up to December 31, 2018. It is up to your department policy as to whether or not those expired persons are permitted to go through the new or re-certification version of the user course.
Use the following links to find information on updates, the list of requirements, how to apply, user courses, and user tests: