Is there a way to set the lifecycle for a manual snapshot in AWS RDS? For the automated ones, there is a time that can be set, but I cannot find anything for the manual snapshots. Thanks for the help.
There is not. From docs:
Unlike automated backups, manual snapshots aren't subject to the backup retention period. Snapshots don't expire.
It means that you would have to develop your own, custom solution for that. For example using a lambda function which periodically is invoked and checks for old snapshots to remove them.