Ah, good point, I hadn't thought it out fully. Yes, I'll set it to epub and leave it there, since I clean up all books as soon as I buy them. If the book has an obviously wrong page count, I'll just convert to epub and do it again. Now that I've got my full Calibre library with page counts, the process is hardly onerous. Almost all my books are mobi first, with the exception of the occasional public library book or Kobo book, so I don't keep a lot of ePub in my Calibre library, but it's not a big deal to add them as necessary.
Thanks for the plugin!