Safety Net

My knee-jerk reaction is to agree with you, because it seems like this policy would punish money hoarding and therefore keep money circulating.

Then I thought about what I would do if I had a sudden large influx of expiring cash, and quickly decided on buying illiquid assets (stocks, bonds, property, a couple fast food franchises in an underserved-but-growing area, etc) which is pretty much what the wealthy already do. The World's Richest Manchild doesn't have $300 billion in cold hard cash sitting around, he has maybe a few million in easily-accessible funds and the rest is tied up in investments (that's why he had to borrow so desperately to get the $44 billion to buy twitter - he couldn't quickly cash out his stock investments without cratering their value).

If money expired, the rich would continue to do what they already do - turn their money into long-term investment vehicles. The worst off would be the people who are in the middle - not doing so bad they have to spend every penny they make right away just to stay afloat, but not doing so well that they can invest in illiquid assets (either because they don't have enough left over after the bills are spent to realistically be able to invest or because they need a safety net in case the car needs to be replaced in a hurry or a tree falls through the roof or the hot water heater busts and ruins the floor).

'Expiring wealth' is something that would do society good by forcing the wealthy class to re-invest in their communities and peoples, whereas 'expiring cash' would just hurt those who would otherwise be on a path to being able to retire someday

Generational wealth is an area where this money hoarding really, really goes wrong, because then it's lifetime after lifetime of the accumulation and hoarding of wealth. So obviously one change I would strongly support is extremely high tax on inheritance income.
But we need to separate money from wealth, I think. Because if it takes all of us working together to generate that wealth in the first place, there is simply no possible excuse for not sharing that wealth equitably. As long as money=wealth, I'm just not sure we'll ever really accomplish that, though.
Billionaires have tons of debt they would have to rectify before they stabilize. Then you assume their liquid assets would be reduced and they would have to find ways to generate more liquidity to maintenance their properties.

Many indigenous americans including the Aztec and Mayan cultural groups used cacao as currency. I can't say if it was intentionally a method to reduce wealth hoarding but it did have that effect.

That is literally what inflation is for. Central banks try to keep inflation at around 2% to discourage hoarding money.

This is not what im talking about and they are not 1 for 1 analogous.
- What are you talking about than?
  
  Hard expiration date tied to the day the currency was created.
  
  Isn't that almost the same thing? No way a dollar bill that is 1 day before expired would have the same value as a dollar bill that expires in a year.
  Or do you except a shop would have to accept a bill that expires in 10 seconds and they won't be able to do anything with it? Would you be fine if your employer paid you with bills that expire in 2 days?
  
  Well, its a thought. There are a lot of variables to capitalism. Just thinking of ways to improve the system if there are people who are dead set on keeping it forever. Maybe it should lose value. If, say it was a 50 year expiration date, the exchange that generated the value has long since past.
  You could also implement a buy back where the government gives you a flat rate on expired currency or a tax write off but you have to meet a minimum threshold.
  To me its important to recognize that money is what we say it is. We can do whatever we like with it.
  The biggest problem would be the immediate devaluing of the dollar, countries participating in our economy would attempt to purchase other currencies. So in that light it would be infeasible but maybe there are ways to transition.
  
  Again, at 2% yearly inflation, the money would have only 37% of its original value after 50 years. And inflation tends to get higher.
  People who "hoard money" usually invest it into something.
  
  If you think thats fine, thats ok. We arent changing anything here today and most likely ever. So if you wont engage because you think your going to teach me something today, jokes on you.
  
  What are you talking about? What do I think is fine? And how am I not engaging?
  
  Will you hear me out?
  
  Sounds like something that would be trivial for the wealthy to circumvent while being very expensive for the poor to do the same. Someone with the means can just pay someone to continuously refresh their money with new money. Unclear on how people will deal with transactions when different bills have different values from what's written on them.
  
  Why would poor people have difficulty living with this change? They live hand to mouth.
  
  They live hand to mouth.
  And they'll stay there if they can't save up any money.
  
  If the expiration date is 25 years? 50 years? 100 years?
  
  Most likely you'll be getting the older bills that are close to expiry if you're poor. It doesn't matter how much time they're given when they're minted.
  
  If they spend at around the equivliance of at new minted bill and youre not trying to save them, what does it matter?
  If you are trying to save youre not keeping hard cash youre investing it. So then we would see a lot more investment spurring on growth.

I’ve had an idea for a book, where the protagonist is a “classic build your fortune” type dismayed at the way capitalism is failing, who ends up making a currency like this; wanting everyone to make money and then spend it by the end of the month; somehow allowing the recipient to get a new extended deadline.

I have some curiosity for where the concept would go. In the story as well it’s imagined that some oligarchs will find ways to abuse the system and hoard it, but in some other cases it might trigger interesting movements.

money kinda already does expire. if you just let it sit around for long enough, it will devalue over time, typically around 2% per year. It's called inflation.

Nobody really hoards wealth by hoarding lots of paper money. Except maybe foolish people trying to save up for retirement that way. (they will make bitter experiences)

Wealthy people invest all their money into company shares, houses/apartments, or gold. That's actually why we see the price of these things constantly increase: Because the wealthy don't know where else to put their money, and so they buy these things, which creates demand for these things, which constantly increases the price for these things (by the rule of supply and demand).