They also have a limit on the number of active credits you can have. I luckily found this out via someone else. But yea that part of Audible sucks massively. But I wouldn't be shocked if you emailed customer support they would just give you the credits, it's Amazon after all. Also, if you sign up and the system doesn't say you're eligble for a 30 free trial, customer support will give it to you. I found that one out when my payment method wouldn't work and I cheekily asked and they hooked me up.