> That's like saying: "don't make backups, just don't screw up."
That does not even belong in the same category. Data backups in computer systems are cheap, and people/organizations not doing them even cheaper!
On the other hand, doctors don't make backups of the gravely ill[1] before a dangerous surgery. That is beyond our current capabilities, so "do not screw up" is as good as it gets.
Yet another example, civil engineers do not make backups of skyscrapers[2] before doing maintenance work, even major maintenance work. While technically feasible, the economic cost would be prohibitive.
My gut feeling is that a "backup planet" would fall somewhere in between cases [1] and [2].
That isn't even close to the best option. That's like saying: "don't make backups, just don't screw up."
edit: to be more specific, "make makeups, but also try not to screw up"