The only time you really need the fan is when you are delayed in getting on or off the track. My ITS car has a switch and when the guage goes up sitting in the pits I turn it on.
When I build the SE30 car I plan keeping the aux fan with the low temp switch as well as a manual override when I want it. I am not sure if it is a two speed fan like was on my E24. If it is I will most likely wire in two switches so I can turn on high as well. I found that if you go straigh to high it sometimes blows the fuse.
Good Luck
Michael O.