There's also the case where the hardware has failed but the system is already up so it just keeps running. It's when you finally go to reboot that everything falls apart in a visible manner.

This is one of the reasons I am not a fan of uptime worship. It's not a stable system until it's able to cold boot.

Say you have a system that has been online for 5 years continuously until a power outage knocks it out. When power is restored, the system doesn't boot to a working system. How far back do you have to go to in your backups to find a known good system? And this isn't just about hardware failure, it's an issue of configuration changes, too.

I also notice that people with lots of experience with computers will automatically reboot when they encounter minor issues (have you tried turning it off and on again?).

When it then completely falls apart on reboot, they spend several hours trying to fix it and completely forget the "early warning signs" that motivated them to reboot in the first place.

I've think the same applies to updates. I know the time I'm most likely to think about installing updates is when my computer is playing up.