

I assumed most people were spending money to see a doctor, regardless of their insurance status, because insurance almost always requires co-pays. If you are insured, you are (hopefully) paying less to see a doctor than you otherwise would have, but you’re usually going to be shelling out money for the doctor’s visit either way.
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