The fans will be on whenever there is insuffecient air flow to keep cool, this will certainly be the case when driving if they have only just come on due to a stoppage and heat build up, mine can take up to 1 mile to go off after start driving again, if you have the wind deflector plate between the std rad and intercooler, this can easily be 10 miles!!, and yes I know this as I have a fan light, as well as it being recorded, first thing I did with std 4wd i/cooler was rip off the deflector, when needing the coolest air through the cooler you will be going fast enough anyway!!
tabetha