You can play with the M106 command to set up the board cooling fan like setting a minimum speed and tying it to the MCU temp, so that if it's blowing across the drivers you get adequate cooling. A shroud over the board that forces the air to travel across the drivers on both sides of the board is best.
I used to try and get fancy with it but in the end just use a command in the start gcode to turn on the case fan at a set speed and then turn it off again at the end of the print. I got tired of the hysteresis ramping the fan speed up and down constantly during the print.