In the IT Industry, that is called REDUNDANCY. Works well for companies and organizations that want to ensure Continuity of Operations. But way too much for mere mortals like me.
My black book hasn't needed REDUNDANCY and has maintained Continuity of Operations since 2002 without batteries. The past 5 year's logs and calanders are available in a single file folder, and I've spent aprox. $6 per year for replacements. Oh, and I have to imagine that since it's worthless to anyone but me the odds are good that if found it will be returned.