Depends on the wood. For harder woods like walnut and maple 5 - 10 minutes seems long enough as they really do not soak in a lot even if left for hours. For softer woods like pine and poplar I do about 30 - 45 minutes.
Make sure you do not store the oil / poly in those bags long term. Left long enough, the finish tends to break down the bags. Also I only use a bag one day. It will handle multiple batches done in a day but not multiple days.