i shut mine down between 340-350 degrees. i have a bd cool down timer. truck shuts off automatically when the magic temp is reached.

 

What P Kennedy is trying to say letting you truck idle and allowing the oil and glycol (I think these 6.7's are glycol cooled as well) to circuilate through the turbo will remove the heat if you don't what Kennedy said will happen.
P kennedy the KW COE in you avatar looks good.

 

Recent failures are from soot and possibly cooked hydrocarbons. The owners manual gives guideline for cool down which may or may not be correct...I also watch my EGT and listen to my engine. Running the EB results in higher vain protrusion of the VGT and reduces the soot buildup...During regen, boost increases slightly thus exposing the extended turbo vane to higher temps reducing soot. The result of the higher turbo temps is longer cool down. My post turbo temps reach as high as 1200 degrees. When this happens, the turbo is still producing boost at idle...If you listen to your engine, you can hear turbo winding down...Cool down time is a function of EGT