Is the Amazon EC2 instance id unique forever?

I asked Amazon, and this was their answer:

"Instance ids are unique. You'll never receive a duplicate id. However, the current format of the instance id is an implementation detail that is subject to change. If you use the instance id as a string, you should be fine."

It's important to note that you will never receive the same ID twice. However, since you can't connect to other people's instances, this will probably be sufficient.