When should vault keys be rotated?

Vault keys should be rotated when there is a significant event that could potentially compromise the security of the keys, such as when migrating to a new data center. This is because the keys may be exposed to new environments and systems, and rotating them ensures that any potential exposure does not result in a security breach. Additionally, periodic rotation of encryption keys is recommended to maintain the integrity of the encryption and to adhere to best practices for security1. References:

CyberArk Docs: Credentials Rotation Policy2

HashiCorp Developer: Key Rotation