All fiat money eventually succumbs to hyperinflation
Which is why this is true.
But I doubt there aren't any currencies around from 1000 AD that haven't suffered that fate.
A decade? 2? a century?
When an entity (e.g, the government) decrees (which, remember, is what the word "fiat" means) that some piece of paper or entry in a database is "money" is when the trouble starts.
I prefer my money to be a medium of exchange and account as well as a store of value that I can trust which, by implication, means it cannot be decreed to be so by some "authority".