With a single account, it is possible to use a single credit an unlimited amount of times without having to go through chat/support to get the credit back.

1) Go to amazon and login with your audible username/password
2) Find the book you want and click the "Audible" purchase option
3) click the purchase option (using audible credit). Leave the tab open on the order confirmation screen as you will need this later
4) open audible in a new tab and download the book from your library
5) after the download is finished, go back to the amazon tab
6) you will see a cancel order button on the right of the page. click it.
vuoala. you have the book and you get the credit back. This will work indefinitely.

Note: Make sure you do steps 4-6 in a timely manner. if you wait too long to do these steps (maybe 15 or 20 minutes), the cancel order won't work and you'll have to use the chat to get the credit back.

nice sharing

great idea i have another one , you can also create unlimited trials with the same cc , i suggest using a 20 dollar disposable visa card from cvs , the trick is if you create an account from amazon so you get 2 audiobooks instead of 1 , then use a fake cc to create your account ,http://www.getcreditcardnumbers.com/ then when you get on the audible webpage it will say that there is a problem with your card , just replace it with the real card number and they will give your 2 credits back , then you can return the books back 8 times or use the method above , but when you run out of credits just cancel uninstall audible manager and reboot cpu , then create another account with same method. the trick is that they won't let you use the same cc if you use it the first time , but you can replace it with the same cc over and over.