I live in Texas. I've had mine off for Years and the only time I ever thought that it would help was when I was in Colorado in the Rocky Moutain National Park, on a steep road, on the side of a mountain. My car vapor locked in the thin air up there. The fan might have helped in that situation, might not, but I got the car going again by putting snow on the fuel rail.
Other than that, never noticed it was gone.