I've gotten one of those emails and thought, OK it's gonna reboot, not a problem for that instance, has no persistent data I care about. Then it kept running,

I've gotten one of those emails and thought, OK it's gonna reboot, not a problem for that instance, has no persistent data I care about. Then it kept running, but there was no way to reboot it from EC2 console or ssh, so that was a bit of a problem, had to get support to do it. Moral - reboot it yourself at a convenient time.