After rinsing my prints, and processing in hypo-clear, all I do to wash my fiber prints is two successive 30 minute soaks in my print washer, without running water.
At any rate, if your prints are soaking for a long time, it would be a good idea to change the water when you can, especially if the prints are not separated.
Also, whether or not the prints will survive such a long soak depends somewhat on the brand of papersome are much more durable than others.