Like some others that have posted, I rarely see that part of my Amazon account. I do occasionally check for updated books, but that's it.
I have about 3500 books in calibre. They are organized (for the most part
) so that I can easily find what I want (whether a specific author / title, or genre, etc) at any given time.
I do not permanently delete books. I do have an archive library, but that's to store originals of omnibuses / collections that I split into individual books, that sort of thing. My main library has search filters that I use to hide / show books I've already read, books I marked as did-not-finish, etc.
It doesn't matter if I never get around to reading them. I read in so many genres that it's always a possibility that a particular book will get read at some point, and that's enough reason to keep it. It's kind of like my music collection. Nearly 20,000 tracks from nearly every genre you can imagine. And each on is there because I wanted it there. If I'm in the mood for Classical, it's there. Blues? Got it covered. Demonic-sounding surf guitar extravaganzas? Absolutely.
I totally understand deleting books you know you'll never read. I just don't think I have any that I can say that about with 100% certainty. Just in case you thought I was screaming in horror at the idea of someone deleting a book. I'm not.
I just don't do it myself.