This thread motivated me to move a few hundred books to Amazon's Trash (thanks BearMountainBooks!). The only reason to move any to Trash is to speed up loading the books when going to Manage My Kindle. Several months ago I permanently deleted dozens of books and I regretted eliminating a few later. One self-published was picked up by Thomas & Mercer, so then I wanted to read it.
Now I move books I doubt I will ever read to a Calibre Vault library (a suggestion that also came from MR). My main library is comprised of books I hope to read. When I enter a book into my Calibre library I assign a priority category. I also list the price paid in a category. It is then easy to sort and find books.
I don't expect to read all the books I've acquired. But I love having so many choices. Browsing through Calibre is like wandering through library or bookstore stacks.