I don't think that refutes OP's point. 10^12 is not that much, actually. That would mean that everyone in the world today gets only ~100 numbers (not even including offspring situations).
> Plus, the population that is eligible for credit doesn't equal total population of the planet.
True, I'm talking about a hypothetical "maximal usage" future.
Sure, it's not ipv6 level address space (2^128), but ~10,000,000,000,000,000 possible card numbers seems like it should last many lifetimes, especially if you consider that card numbers could be recycled/reassigned, and if we ever approached the point where running out of numbers was within imagination, we would come up with a new scheme that allowed for a few new digits. My guess is the credit card itself as a concept will be long gone before the numbers are all used up.
> My guess is the credit card itself as a concept will be long gone before the numbers are all used up.
I agree. Products like "privacy.com" hint that we could be approaching a "new number per purchase" meta. Even in that edge-case, if one million issuers get to have 10 billion numbers each, that would leave tens of concurrent purchases per person per issuer for an issuer with a billion users. A monopoly-level media site that lets you open a paid-subscription to multiple people could easily end up needing tens of concurrent cards per user. It seems like issuer-to-issuer number recycling would be required for sure.
Credit card is 18 digits, which is where the 10^12 comes from.