Why doesn't currency have an expiration date?

Update: I think the US dollar should have an expiration date on it. Every year bills would be printed with a two-year expiration date. After the second years banks would remove old bills from circulation automatically and a notice would be sent to all citizens reminding them that they have 6 months to bring their currency... show more I think the US dollar should have an expiration date on it. Every year bills would be printed with a two-year expiration date. After the second years banks would remove old bills from circulation automatically and a notice would be sent to all citizens reminding them that they have 6 months to bring their currency to the nearest bank to exchange them. I also think that there should be a limit on how many bill can be printed. It should be based on the GDP of the country.
Update 2: Denominations should be based on how useful they are. If I cannot buy anything with pennies than they should be discontinued. the denomination should be 1's, 10's, 100's, and 5's, 20's, 50's and 2's should be discontinued
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