An announcement regarding the Pygoscelis Papua Linux AMIs that will start in September 2016:
The rolling wave for Pygoscelis Papua Linux AMIs will be changed to three months, so it will keep the two most recent builds. When the 2016-09 release comes, it and the 2016-07 release will remain while the rest will be retired. The retired AMIs will remain on us-east-1 for archival purposes. If you wish to copy any of the old images, our articles HowTo: Copy EC2 EBS AMIs Between Accounts and HowTo: Move an EC2 EBS AMI From One Region to Another may be of use.