Periodic reboots are actually a PCI requirement for payment terminals heh, basically every point of sale on the market reboots every 24h.
Seems like a good defence in depth strategy. These days most systems have a pretty good boot chain security, so after a reboot you know the system is in a valid state and any potential malicious changes have been flushed out.
This is so damn sad. I don't fully get why I have to reboot after kernel updates but accept it, but just every 3 days? Why?
How do you expect to swap out your kernel without restarting your machine?
Don't know about apple, but on linux you can live patch a running kernel with security updates (kpatch/ksplice/...).