I think backing up and then encrypting the whole folder would be a good idea. Just decrypt it if you intend to use the wallet. I use Cryptomator + Veracrypt for this purpose. If you want to store it in a USB then it would be a good idea to also zip it with a password. Even if you are hacked there will be 2 or more layers for the hacker to get to your coins.
Cheers FURY, was always weary of storing the file on a cloud service etc, i do have it zipped passworded on a few USB's/SD and that zip is in a passworded folder.
I just save the WHOLE multibit folder located in the position of my first post as i do not now which private keys precisely to save (makes no difference anyway i suppose as they are ALL removed from my pc).
I still like the look of the KeepKey though for ease of use and it's only $99 (still overpriced !!!).