If there is validity or expiry for every currency same as day to day life needs, then people will make use of it and exchange to new currencies at the right time. This way everything can be made to be in circulation rather than getting accumulated for years. Here black money can also be avoided.
This is very funny. It has never be heard of to have fiat with expery date and it will not be economical to even have it because it will require regular printing of cash even when the government want to control inflation by withholding money circulation it will be forced to print it. If the aim is to beat criminals or those who pile up cash they do not use by putting expery date to cash, you can trust that criminals will find a way to beat the system. So this will not work.