Fans....? What fans? We dont have no stinkin fans man... J/K What kind of fan is it? I worked at FAL for a few years, and depending on what fans you are talkin about, some are not made to run for more than 1 hr before they overheat or burn up. Also if you have a constant fan (if its fairly large) it will draw alot of power from your electrical system, and can put strain on a stock system, (which is why race cars have HO alternators). So what are you trying to do?
P.S. A small fan or 2 small fans, on a tranny and oil cooler will be alright, but anything larger than that may cause power loss and problems.