Here's something I'll bet you didn't know. If you leave jeans that have gotten too small in the waist folded up and stored away for a long, long time, they will get longer in length. I know this because some years ago I had to resort to buying new jeans made in China. We all know the Chinese size clothes a little smaller, so I was forced into buying jeans with a larger waist size. I saved the old jeans, thinking I would someday be able to get into them again. Well, that day came. I pulled them out of the closet, put them on, and was able to fasten the top button easily.
However, when I looked down, the ends of the jeans legs were bunched up around my ankles big time. They certainly weren't that long when I put them in storage, so this is how I know jeans get longer when stored over a long period of time.