It costs nothing to maintain the credits, and in fact, the cost of providing the service the credits are for goes down over time (as inference speeds increase).

It is arguable that taking money for a service and then not providing it is immoral and unethical.

Credits that don't expire absolutely cost something -- it makes the financials look worse.

See backprop1989's comment [1] from when this topic was discussed in august 2025:

> Accounting rules. If the credits last indefinitely, any unused credits cannot be counted as revenue. Ran into this at my last company when we signed a big contract and gave them hundreds of thousands of dollars in non-expiring credits. Our accountant went nuts when we told him.

[1] https://news.ycombinator.com/item?id=44793827