I do use RMAN duplicate for refreshing our 1 TB DB. It takes about 10 hours. However, the best way in my opinion to handle this is at the storage level. Most storage systems now offer features to snapshot your databases. On this same DB, it took 10 mins to do along with the archvie log needed for recovery. The clone procedure takes near 1 hour to complete. You just cannot beat that.
On the other hand, I do like the RMAN way because it is the ultimate measure of how good your backups are. It feels good to know that you have good backups you can rely on.
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