Well they're almost all monopoly currencies (not a reference to the game) that are run by people who can increase the money supply.

So basically we can just plug your 27 year figure into a probability density function to find out how many more years we can expect the USD to be kicking around? How many years does it have left, at varying levels of probability?

The incentive of a monopoly is to underproduce.

The Fed and a government that likes to spend has proved otherwise.

Not at all. If production of dollars was competitive, they would be priced near the cost of production. I'm not saying there are no valid critiques of USD and our monetary system. I'm saying that it is not bad for the reasons monopoly is usually bad.