This Is How Long Your Cash Physically Lasts
While the legendary cashless society may eventually become reality, for now cash is still a pretty useful thing. There are still scenarios in which you need some paper money, whether it's a local restaurant that only accepts cash to an extended power outage that renders your digital payments useless. As a result, most people keep at least a little cash on hand for emergencies. Emergency cash is best forgotten until it's needed in order to resist spending it all over time, but this leads to another complication: Cash doesn't last forever.
While U.S. law explicitly states that any paper money printed after 1914 is legal tender, meaning your money never "expires," like everything else in this world it will eventually spoil. In fact, in-circulation paper currency has a defined lifespan of between 7-23 years, depending on its denomination, because of the wear and tear of handling. And cash is constantly being destroyed by the Federal Reserve and replaced with fresh bills to combat that degradation.
But what about cash sitting in your desk drawer, under your mattress, stacked in your walls, or buried in your backyard? If the power goes out and you go looking for your stash of cash, what are the chances you find nothing but regret instead?
How to properly store cash
If you store your cash properly, it should last longer than you: as long as 100-150 years. The key is that "stored properly" business. Cash needs to be kept dry, away from the sun, and protected from other elements. If you're aiming for the upper range of your cash money's longevity, you need to store it in a climate-controlled space (like a safe) in double-wrapped plastic or Mylar sleeves. Do that and your grandkids will be able to spend that cash.
If that's a bit much for your emergency pizza fund, your money could be gone in as little as a few months, because there are a lot of things trying to destroy your cash.
Pests that can destroy cash
Nature is metal, and there are creatures roaming this earth that can eat a surprisingly long list of things--including cash. U.S. currency is made from 75% cotton and 25% linen (a combination called ragstock). This makes it durable, washable, and long-lasting--but it also contains cellulose and starch, which makes it an attractive meal for a lot of pests:Silverfish. If you have cash in your house and see some silverfish scurrying about, worry. They will be attracted by the starch and happily munch on those bills. Your first sign will be some random, uneven holes in the cash. Termites. Termites don't just eat wood--they'll make a meal out of anything with cellulose in it. That includes that cash you stacked up in the walls like a drug lord. Mice. If you've ever suffered a mouse invasion in your home, you know that these rodents will eat anything. If some mice stumble over your cash hoard, they will totally eat it.
If you bury your cash like they do in the movies, you'd better wrap it up really, really well, because there are even more bugs and other things that would love to eat it--and your stash would be gone in about 5-10 years.
Mold can destroy your cash, too
Mold is industrious stuff and it will grow on almost anything under the right conditions. If your money gets damp due to a flood, a spill, or just very humid conditions in its location, mold can start munching away at your cash within a day or two--and start doing visible damage within a few weeks. If undiscovered, that mold will eventually destroy your currency--according to paper scientist Douglas Cobb, that process could take as little as 200 days.
Keeping some cash on hand is a good idea as a hedge against emergencies, but it's also a good idea to refresh that stack every now and then to defend against the forces of entropy that seek to bankrupt you.