I think there is some tribal procedures creeping in here. In the airlines I always released the brakes when the chocks were in place. I left the cockpit and went on with my busieness leaving the aircraft in the capable hands of the mechanics. End of story. In my corporate life, operating a B757 and 767, I did sometimes leave the brakes on as the ground crews were usually not very disciplined, or in many cases simply not around. The thought of waking up in the middle of the night, wondering if the airplane had moved for some reason was cause enough to not take any chances. Since no one had access to the flight deck during these layovers, there was not much question about someone moving the aircraft.
