I seem to have an irrational fear of not having enough binding for a planned quilt so I measure it out a bit too generously. Doesn't help that I don't actually measure it, I run it around the edge of my quilt with ample inches allowed for mitering corners. As a result, I too end up with leftover binding. Sometimes as little as 18" but usually much more. I also have them saved in my scraps in a ziploc baggy marked "bits 'o binding". I will use them in a scrappy quilt as they are already pressed right sides together and ready as binding. I can't be bothered with pressing them flat again to use as strips in piece work, I get enough of those when I am doing regular cutting for patchwork.