There is an interesting concept in mathematics: orthogonality. Basically, two sets of shapes are orthogonal if everywhere the intersect at right angles. Vertical lines and horizontal lines are orthogonal, as are the set of all lines running through a point and the set of all circles that have that same point as the center. Even latitude lines and longitude lines are orthogonal.
I think this concept applies to prepping. What it boils down to is minimizing overlap. Specifically, if you use scenarios to guide your prepping, try to make the scenarios as different as possible. That way you can be better prepared for what actually does occur.