so lets say a livepatch comes in and my current running kernel gets patched, and I don't reboot the server because I don't need to any more. What happens if weeks/months/whatever down the line another livepatch comes in, and weeks later another, etc? Is this situation sustainable without rebooting ever?
The only way I could see that being the case is if each livepatch patches the running kernel to be exactly what it would be if you did the normal apt dist-upgrade
to get the latest kernel and rebooted, but my impression was that livepatching only fixed high and critical security issues and left everything else untouched.
Or, do they just test each livepatch against a variation of older base kernels + varying numbers of previous livepatches made to them? If this were the case I'd guess there's a limit to how far back they would test, and that eventually you should reboot to make sure your base kernel is one that the livepatch was tested against?