I haven't really paid much attention, but I'm pretty sure CentOS/RHEL only do kernel updates with distro updates. If so, it's about once or twice a year: https://access.redhat.com/articles/3078
In practice, my companies have done them less frequently. Kernel packages are less often about security patches and more often around a magic combination of kernel+GPU driver+software--I think one of them paid Red Hat for custom cuts.
As for maintaining a personal machine, that distro would probably suggest rebooting more often than RHEL (you'd also have to effectively logout/"restart" for any core package for your Desktop Environment or X). I haven't measured, but I feel like my Synology gets updated every few months.
As for the impact of rebooting. Windows Updates (and macOS updates) are more than just a reboot. It's often an unknown amount of time. Even for a normal reboot, it's really really nice to just leave everything open so you can pick up where you left off. Personal or work it's more than just a browser, but terminals I have open, shell history, vim sessions.
If I have a few tens of applications open that all have their own separate state that is lost on reboot, then itβs fairly annoying to reboot because one thing updated.
Maybe it's what exactly you do then/how. I.e. apart from a REPL session in which I maually typed a bunch of commands, I don't seem to have that problem. Editors/IDEs/browsers all persist open documents/view state etc between runs.
Fair enugh, but depending on what distro you run that seems to be fairly often as well. Like, more than 'a few times' a year.
Then again if you dont run a server for which downtime is a true loss, or something alike, is rebooting that much of a problem (honest question)?