There are only 24^3 possible combinations of 3-letter file extensions, 34^3 if we start mixing in numbers. And they potentially will need to be constantly avail

There are only 24^3 possible combinations of 3-letter file extensions, 34^3 if we start mixing in numbers. And they potentially will need to be constantly available for decades to come... We should probably use more sparingly to prevent a repeat of the IPv4 situation.