Expiration because selling something that never expires is a permanent liability.

My friend had the idea that I could make all credits expire in 2 years (for the liability issue) and simply discount the cost/credit for larger numbers purchased at once, perhaps that would make it less confusing with the 7 days and 30 days options available currently? Perhaps combined with an option to repurchase the same amount automatically once your previous purchase expired/was used up would be better?

Thanks for the feedback, I thought the structure was actually customer-friendly (no subscriptions and lots of choice depending on your usage), but obviously I'm wrong from the feedback in this post. I'm definitely hearing that that's something I need to change.