[RyanN]

Victor fans are not required by FIRST, but I'd definitely recommend them. The FETs work by switching the power to the motors on and off very quickly, which creates the heat. In reality, as I understand it, a FET will get hotter as the motor gets slower with the same amount of force needed to rotate it because it switches the motor on and off so fast (try touching a wire on and off of a battery that is connected to a CIM motor... the wire will get hot). The fans keep the FETs cool of course, and FETs are more efficient the cooler they are, and WILL release the magic smoke and stop working if you do not put fans on. I do realize that you said that you will have fans around your case, but I do not think that is enough. I would cut holes specifically for the fans and have some fans pull the hot air out of the case or move the victors to a different location.

Either two or three years ago at LSR on team didn't connect their fans, and their robot would only run for 30 seconds before stopping.

It's your choice, but, personally, I would recommend using fans.