I have a vast Audible library. The selection from Amazon Audibleis probably the largest audible library in the world. I purchase the prime membership which gives me 24 credits fot around $230, with a year to use them. 1 credit usually buys 1 book. Once you buy it, it’s yours to keep. You have a year to use your credits. They also have 2- or 3- for 1 sales throughout the year. And, they also have books that sell for less than the price of a credit, so don’t waste credits on lower priced books. I normally use up my credits before they expire and renew them early.
I go the same route you do with the yearly membership. Only wish they had a larger number of books for the year price. I’ve found some obscure books that I had been recommending to friends (The Lost Prince, by Frances Hodgson Burnett, Regency romances by Georgette Heyer, Brewster’s Millions by George Barr McCutcheon (only wish they had the Graustark books)). Revisit your childhood with the Albert Payson Terhune books, or Walter Farley. With the restrictions in numbers of books, I end up listening to favorites (like the W.E.B. Griffin military books) four and five times.