2.2.3 [W3C-P3P1.0] Section 22.214.171.124.3, Requesting Policies and Policy Reference Files
Note that it is impossible for a client to accurately predict the amount of latency that may affect an HTTP request. Thus, if the policy reference file covering a request is going to expire soon, clients MAY wish to consider warning their users and/or revalidating the policy reference file before continuing with the request.
All Document Modes (All Versions)
Users are not warned if the P3P policy reference file is near expiration.