Agreed with Tracy here.
Some hobbies may stay forever and others might change overtime (kind of like your favorite foods). Don't be afraid of losing interest, because that might just mean you found something you are more passionate about in life, and that is a good thing.
However I would encourage you to see what it is about books that you truly enjoy, is it the ability to enter a new world? Is it the creation of a great story that captures you? You might be able to find another hobby as an author, writer, illustrator or more if you can understand what it is about your hobbies that you really like.
No need to be afraid of loosing interest in a collection or a hobby; if it no longer brings you pleasure step away from collecting for a few months and revisit later in the year. Sometimes we out grow our hobbies and develop newer interests that better feeds our souls. In the meantime, hold on to your books or lend them to your friends and neighbors to enjoy.