public void setMaxPurgeInterval( final Duration maxPurgeInterval )
    {
        this.maxPurgeInterval = maxPurgeInterval;
    }
Returns an estimation on how long it takes for all data that arrived before a certain instant will have become
available in the data store. When data is immediately available, 'zero', is returned;

This method is intended to be used to determine if it's safe to construct an answer (based on database
content) to a request for archived data. Such response should only be generated after all data that was
queued before the request arrived has been written to the database.

This method performs a check on the local cluster-node only, unlike {@link #availabilityETA(Instant)}.

@param instant The timestamp of the data that should be available (cannot be null).
@return A period of time, zero when the requested data is already available.
xmppserver/src/main/java/org/jivesoftware/openfire/archive/Archiver.java