Originally Posted by
planemechanic
And my original response was reflecting that condition. All power off, every day, at least once if not more. In fact one of the methods of troubleshooting software issues is to power down and restart the airplane. Sad, I know, but it works, especially with nuisance messages. I seriously doubt, though have no way to prove, that ANY commercial airplane has every been powered on continuously for even one week, let alone 248 days. It just ain't gonna happen.
There are many systems where "powering down" does not 100% power down.
I would be morally certain that all the main and aux power is off "overnight", but that does not mean that some small power is not left to keep some firmware powered up.