There is still on going debate as to the length of time that a certificate is valid, and indeed if there should ever be an expiry date.

The reason for the inclusion of an expiry date is to ensure that the competence of personnel is checked on a tri annual basis to ensure they are still competent in the latest safety, operational and technical requirements.

Many people leave the industry and consequently lose some of the skills that are required to perform in a safe and competent manner.  The re-certification process attempts to prevent this occurring and consequently ensures all individuals working offshore have their competence checked against industry standards.