Bought 12 credits and because I only needed a few didn't log in for a year so they just took my money and and can't use any more credits. When I complained they said oh it's mentioned in FAQ's and everyone else uses them immediately. Sounds like a con to me!
Why not tell customers that that is the deal that they need to log in, why not send a reminder email that it's due to expire, oh yes that's right because it'll make them more money!