Causes problems with IT maintenance over night ?

Nah, wake on lan.

Or have one night a week as maintenance night. If it's missed, the user looks at a locked screen in the morning waiting for updates to complete. And that's at a law firm. With partners. Who WILL get rid of the WHOLE IT department if they so much as lose a second of billing time while unimportant trivia like security patches are applied.

As for boot up time - use Hibernation.

Or better still have a power saving background task that hibernates after 2 hours of no activity (see, also save power Friday lunchtimes), except during those periods when you know your critical updates are going down.

C'Mon folks. Get with the 21st century.

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