> we can’t have unlimited liabilities stacking up forever
The liabilities are completely offset by prepayments from your customers though. Even better, you can earn interest on the deposits without paying any out.
If you just dont want the liabilities on the books, issue refunds. Expiring credits feels like a cash grab.
It's just basic bookkeeping, storing money over fiscal years is a nightmare to manage. (At least over here, dunno about whatever country Openrouter is based in)