That period may last surprisingly long. People can lose confidence in currency, but their faith in precious metal seems to last longer. I can imagine that once people have lost hope that any semblance of a normal economy would return, gold and silver would lose their value fast. But has that ever happened in history? What I'm saying is that thus far humanity has been resilient enough that we've always recovered. Or, perhaps those locations that never recovered just... vanished. You can't create an economy because the situation is so bad, and everyone is just a meal away from starvation. Eventually everyone dies.