You can keep all of the audiobooks in your Audible library even if you cancel your account.
Brad's Deals Editor Michael,
New Audible subscribers can drop the price of a three-month membership from $14.95 to $4.95 by signing up using an Amazon Prime account or a Prime free trial. This three-month subscription gives you access to over 425,000 audiobooks. You'll receive a credit to download one free audiobook every month, regardless of the book's price. You'll also receive a 30% discount if you choose to purchase any audiobook from the Audible library. The normal monthly fee will apply after your three months are up, but you can cancel at any time. If you cancel, you'll still have access to all of the audiobooks in your Audible library. There is no sales tax.