You can compare other discontinued currencies. It’s been about 135 years since Confederate States of America currency was declared worthless. Last time I looked, for the most part, they sell $10 - $100 each. You could say they overall total the face value. Saving them would not have been a good investment at all.
Buying a crate full, at scrap paper prices, a few years after they become worthless might be OK.
Anyone know about Nazi currency?