As we know, with time we add more equipment and racks in our Data Centers. We may even replace or upgrade some systems with latest technology equipment. Few changes to the original plan may also be done to meet the changing requirements. Recertification will help in ensuring that these changes do not lead to noncompliance to TIA standard.
In fact, this is the reason why annual surveillance audits are mandated even within the three-year validity period of the certificate.