Unless you go back to Bartering, Money can't expire, but currency can, such as when an Empire/Country/Political union collapses/arises, new currencies appear. A

Unless you go back to Bartering, Money can't expire, but currency can, such as when an Empire/Country/Political union collapses/arises, new currencies appear. A more recent case being the Euro currency - many EU countries dropped their currency, for Euro. In the process there were losses and gains, since there may not be cross-market consensus in value-conversion. For instance, Real Estate may suddenly be more expensive, likewise groceries, but salaries stay the same. What you could do though (i'm not an economist) is to periodically introduce Monetary and Fiscal Policies that reset/adjust the economy (outside a government's influence e.g. Central Bank + Supreme Court).