You might want to try this thread. A couple of programs are discussed to convert your Audible books to MP3s.
https://www.mobileread.com/forums/sh...d.php?t=288032
There used to be a way via Audible Manager to burn your Audible books to CDs (multiple CDs per book), with a limitation of doing so only once each book. No idea if that's still possible (or desirable).