cacheDuration property

The client-side cache duration.

The client MUST add this duration to the current time to determine the expiration time. The expiration time then applies to every URL queried by the client in the request, regardless of how many URLs are returned in the response. Even if the server returns no matches for a particular URL, this fact MUST also be cached by the client. If and only if the field threats is empty, the client MAY increase the cache_duration to determine a new expiration that is later than that specified by the server. In any case, the increased cache duration must not be longer than 24 hours. Important: the client MUST NOT assume that the server will return the same cache duration for all responses. The server MAY choose different cache durations for different responses depending on the situation.