Well, here is one scary reason against letting it dry. Think of laundry. Suppose you spill something on your white shirt, and don't have the time to wash it immediately. What's the best way to avoid a permanent stain? Should you dump the shirt in a bucket of water and let it soak until you have the time to do the laundry, or should you let the stain dry and wash it later? If you don't know the answer, talk to someone who does laundry in your house. Washing photo paper is not terribly different from washing a shirt in a sense that you are trying to eliminate permanent stains.
Originally Posted by f/stopblues