Like the previous poster, I am not understanding why this is a problem for you at all, and reading this about EANs hasn't shed any light.
https://en.wikipedia.org/wiki/Intern..._and_upgrading
However, if you have DeDRMed books that would be a pain to reload should you actually need a factory reset for an issue, keep them organised with Calibre. Reloading them is then trivial.