I think its smart to be paranoid about losing images, but I haven't heard of a camera zapping both cards. How many images have you lost in the past?
The technology is here NOW to quickly backup your images to a remote device, Canon has a wifi transmitter that is high speed, or you can get a slower EYEFI card to backup up your jpegs. It can back them up as you go, and why worry if it is not instant, if it gets behind, it will catchup when you take a break.
For really important big money projects, multiple backups are made ASAP and kept in different pllaces so a single event like a fire, plane crash, etc will not get them all. Even then, money is not unlimited.