Indeed time is the best answer. When we talk about paper money, I think we talk about cash particularly (paper and coins). Just open any book about history and observe that people has been using cash money for thousands years. And some people think that digital money or cryptocurrency will replace it in nearest future or during our lives? We all can dream that one day will conquer and explore space, everything will be digitalized. But it looks like that we will destroy each other faster than will have first space colony.