Ebooks are a fun hell to order for a library. Many do have an end of life either in the form of maximum number of checkouts or under a license of 1-2 year access. They have all the same restrictions as normal books so patrons still have to wait to access the magic pixel arrangement. Ebooks are also generally just more expensive, even with the limitations. I have seen several above the $100 range, and many of those still have some form of end of life. If you ever wonder why your libraries ebook collection is a little slim, it is because they are incredibly cost prohibitive to maintain.