ISO 17025 accreditation is valid for the length of the specified accreditation cycles. This period varies depending on the accreditation body and sector. The accreditation bodies must comply with the ILAC (International Laboratory Accreditation Cooperation) policy that accreditation cycles must not be longer than 5 years. Typically, this period is four years for some laboratories, but for others, it can be as short as two years or the maximum five years. Accreditation cycles begin at the date of the decision for granting assessment. After that date, accreditation bodies perform surveillance assessments to continually monitored the competency and compliance of the laboratory. A full reasseement must be scheduled, and accreditation granted before the expiry date of the certificates.
For specific information for your laboratory, I advise you to contact the accreditation body you will use for assessment. This information should be available on their websites, as it is policy-driven.