W2R
Moderator Emeritus
If one were the kind of person to do this, the DRM is more easily removed from the ePub format books than from the kindle books. That is, if you want to download a book from the library and read it at your leisure, a device that can use ePub is an advantage.
You could just leave the wireless off once your book is due. The book will remain on your Kindle until you turn the wireless back on.
Usually I remember to finish a library book within the three week period allowed, though.