Trebor, don't we have to keep our bound book for at least 20 years and still record disposal information, etc?
For a C&R holder? I can't say for sure.
I did keep my book, but no longer update it in any way.
I do have other normal records of any C&R related sales, so I could update my book if needed, but if I don't have the license, why would I need to update the book?
I think I could actually destroy it if I wanted, but I'm not totally sure on that either, so I'm not recommending that unless you know for sure.