That aspect was more of a concern than a reported problem. Since getting the 5DMIII it's not been down long enough for me to determine if there is a drain issue....but very happy to hear it is not on the other models. So now just need to get them to be consistent with the firmware configuration settings and not make arbitrary changes to the configured defaults.
The issue I have reported is that this check is done when the camera power is OFF...which may lead to some interesting power drain issues if the camera is left off for an extended period of time (the camera has to check for some condition when the power is off to detect the door opening). However Canon could not confirm that this impacts the charge on the battery.
1 Series already does this and that has no battery problem
I think this is a non issue from a battery drainage point of view