None of my cigar pals has ever seen a need for a fan. They use large (70-120 quart range) clear plastic storage tubs with handles that lock the lid on top. With no fans, and humidifying devices spread kinda randomly around inside, all their cigars are pretty much equally humidified and feel and smoke the same, no matter what position they've occupied in a container.
Therefore, it seems that in decently-sealed containers (at least, like these described), humidity spreads out evenly all by itself.
Hope that helps somebody!