> That being said, do they dump your instance if they reboot the physical server? I was under the impression that "Oh we want to upgrade they hypervisor kernel, your instance is toast", was fairgame/default on Amazon.

Nope. In most cases, you get two weeks warning before a physical host is decommissioned. I've gotten as little as 24 hours (guessing it was a more significant than usual hardware issue).

When that happens, you can just stop the instance, then start it again. That moves it onto a new physical host. If you don't do it in the 14 days, Amazon does it automatically. No loss of data, and just a few minutes of downtime if your startup scripts are OK.