Idle UP
Whenever idling for more than a few minutes it is always wise to increase idle speed. I turn it up to 1200 or so. Helps with ring seating / cylinder glazing, cylinder temp, injection spray and combustion. The bigger the injectors the sloppier they will be at idle, the more important to idle up or shut down.
The effects of extended idling develop over time. There are no benefits to the engine from excessive idling, only potential problems. Of course cooling the turbo down and allowing the temps to stabilize prior to shutdown is good. Excessive is where you go into the diner and come out in a half hour!!
Doug Rees