My fan comes on after doing 70+ on the highway, basically wide open throttle for extended times. The fan kicks on as soon as I slow down on the exit ramp.
The fan also comes on almost constant while doing 1st gear offroading. For normal around town, with occasional stop light the fan never comes on. In fact when I broke my fan offroading, I ran without it around town for a few weeks, and never once did the overtemp light come on.
The overtemp light will come on pretty quick offroad if you are doing tight woods 1st gear single track.