AWS issues unavoidable reboot schedules with short notice on many EC2 instances 12 years ago
Apples to oranges if you're comparing bare-metal to xen/ec2.
If you're just worried about being able to manage your own window you won't have access to a embargoed xen issue before it becomes public. It's the first time they forced a 2 day scheduled event on me, I'll error on the side of caution and take my reboot.