I have a follow-up question on recommended practices for those who keep an original liberated source file of each ebook you buy.

Is there a good reason to keep the original and unchanged version of an ebook source file somewhere in a separate backed up source files folder outside of tools like Calibre, so there's no risk of ever deleting or messing up the original source file?

I can see some value in keeping the unchanged original source file. But OTOH, not sure if folks who have done this find that it's worth it having to keep track of the original source files, plus the copies that you manage/edit/convert in Calibre.