What is the best way to keep logbook entries backed up? What is the best way to keep logbook entries backed up?

Should a photocopied or scanned image on a computer suffice? Can an Excel spreadsheet or other software/apps be used? In case a logbook is lost or (unfortunately) destroyed, should all entries from the backup be rewritten in a new logbook?

Also, when one has 100s or 1000s of hours, spreading over several logbooks, how much importance the older logbooks will have? Would someone go over every page to make sure that this individual actually have 1375.2 hours (as an example)?
The FAA requirements are for the information to be logged, without specifying the details of how it is logged. 

It's OK to use electronic log books, and multiple log books. Scanned images are as good as photocopies. Just print them if you ever need them on paper. Some items are required to be signed, so scanned signatures and endorsements may be necessary in an electronic logbook.

The older the information, the less its importance. Log books are normally examined to see if what you're doing is legal, checking ratings, currency, training and reviews, etc. If you are flying without required night or IFR currency, for example, it is conceivable that they'd want to check previous flights to see how often that has happened in the past. 

An insurance company might want to make sure you've got the hours you claim, but the FAA's interest is to see if you are legal.