The idea of expiring money is more than a century old, and has been tried on a small scale in a few municipalities ("stamped money").
https://www.npr.org/sections/money/2019/08/27/754323652/the-...
https://www.npr.org/sections/money/2019/08/27/754323652/the-...
Main thing that worries me is the sophistication of the control. What I do not want is all economical activity to be corralled into a financial system where states/bankers can see every transaction, take your assets at a key press, and destroy your savings.
State backed currencies seem like a good idea, so do legal alternatives and anonymous payment options like physical cash.