[g_p]

Just thinking aloud here - would you need to disable all automated updates on iOS before doing this, lest the device do a reboot for a system security update, and end up on the lock screen?

There's probably some interesting failure modes when trying to get a modern device to stay connected for months on end, without deciding to reboot for a security patch or similar, or taking an automated app update.

[acdha]

I always have to enter the password to start an install. I’m not sure if there’s a failsafe after some period of time since I usually install day-of but I usually wake up to some nag saying it couldn’t be installed overnight because I didn’t authenticate, and all of my devices are set to install automatically.

[pie314isi]

I suspect it doesn't matter. if the phone is powered and on, it's still doing the iCloud stuff in the background, even if it's locked.

[kevincox]

Note that there is a difference between regular "locked" and the "locked" after a reboot. For the later most of the disk is still encrypted so very little data and few services are operational. You can likely recieve text messages but I doubt much of iCloud syncing works.