I misspoke, it's 1 hour, not 24. Can be found here [0]. Regardless, the upgrade happens _before_ the customer is charged, so unless you put a hold on your system and wait for that invoice to close, you're still giving them access before they've paid (Stripe's system will shown them as having the new upgraded plan before the invoice closes). And with the charge re-tries and back-off they use, if your webhooks aren't listening and reacting, you've still opened up your product to a user who hasn't paid for up to days at a time. I would be very interested to know how you got yours to close instantly, if it is doing that.

[0] https://stripe.com/docs/billing/invoices/subscription#genera...