KMS activation requires periodic re-validation to ensure that software licenses remain valid. Typically, KMS requires reactivation every 180 days. During this period, the KMS client software on each activated device communicates with the KMS server to confirm the validity of the activation. If the client fails to connect with the KMS server within this timeframe, the software may enter a reduced functionality mode until it can be reactivated. This periodic validation helps manage and ensure the proper use of software licenses.