Why is this necessary? Given how fast AWS continues to grow, we will start to run low on IDs for certain resources in 2018. In order to enable the long-term, uninterrupted creation of new resources, we need to introduce a longer ID format. All Amazon EC2 resource IDs will change to the longer format in July 2018.
I already opted in for longer IDs last year. Why do I need to opt-in again? In 2016, we moved to the longer ID format for Amazon EC2 instances, reservations, volumes, and snapshots only. This opt-in changes the ID format for all remaining EC2 resource types