Every time I buy a book at Amazon, it gets downloaded whether I want to read it now or not. The freebees mostly have taken over my library, so I am in the occasional process (an hour or two here, an hour or two there) of making sure that the freebee is DRM free in Calibre and deleted from both my cloud and my Kindle until I am ready to read it. My library is too large to have all at the same time and I do prefer to have entire series loaded at once so that I can not only read each book, but go back to other books to read notes from prior ones.
My Mom's clutter free Kindle is my goal. She has about 125 books on hers, 100% of which are sorted into 8 folders (5 different series, 3 different genres). She is a person who reads a single book from start to finish before moving on to another. She is also not a re-reader. Even her paperbacks go out the door as soon as she is finished.