A few people have mentioned achieving long uptime. What is often overlooked is that it is possible for uptime to be too long.
It is quite possible for updates to not break a running system but make it so that it will break on the next reboot. E.g., a dynamic library gets updated in a way that breaks a server process. It doesn't affect the running server because it still has the old library loaded.
Next time you boot your server process doesn't start.
These kind of problems can be annoying to deal with, especially when your system has an uptime of years and for all you know whatever change broke it could have been in any one of dozens of updates you've applied over that time.
Probably one should have a canary system that is rebooted every day. In a home setup we usually don't hand either the spare machine or the spare time to deal with it, or both.
The easiest way is to reboot after updates. Most updates are not urgent so unless you are having some problem that you hope the update will address wait until a time when it is OK to reboot. Then install the update and reboot.
If there is an urgent update that you need to apply at a time when rebooting would be an issue apply the update and leave yourself a reminder that the system is running a configure that you don't know is bootable. When a reasonable time for a reboot comes around take it.
Me personally, I always reboot after every update. I'd rather deal with the break now while I'm working on it, rather than at some random point. Then I'll know exactly what changed.
I take it a step further. I usually reboot before updates, too. Make sure I won't chase updates as an issue if something else broke.
It is quite possible for updates to not break a running system but make it so that it will break on the next reboot. E.g., a dynamic library gets updated in a way that breaks a server process. It doesn't affect the running server because it still has the old library loaded.
Next time you boot your server process doesn't start.
These kind of problems can be annoying to deal with, especially when your system has an uptime of years and for all you know whatever change broke it could have been in any one of dozens of updates you've applied over that time.