Mt experience has been that once the "silvering out" gets to a stage where you notice it, the rate of deterioration seems to accelerate. (I hasten to add that this is not a scientific evaluation) If you want to retain the prints for posterity I'd advise making copy negatives ASAP before they turn completely black. Make no mistake, this is a terminal condition.

From another perspective, however, that iridescence looks really cool!

Bob