that does not work, you have everything syncronized no recover is needed whatsoever

a export restores you the database but the only way to recover a database to point of failure is by restoring physical backups and applying archive logs

if you have archive logs what is the point exporting every 3, 4 hours??? instead of exporting e, 4 hours you better copy archive logs to other servers or tapes every 3, 4 hours if you are worried about a sevrer crash