The data generated by TAG Metrics can grow quite large. TAG generates roughly 1 Gigabyte of data per 100000 requests, so depending on your traffic these can quickly fill in your disk space.
Also, it is at the discretion of the user to define for how long the Metrics data should be kept since this information is useful to debug issues, find problems or just ensure that the system is behaving properly.
Since data is kept into Elasticsearch, you require Elasticsearch Curator to help you curate, or manage, your Elasticsearch indices and snapshots. It allows you to retrieve a list of Elasticsearch indices, filter them and perform several actions on them.
For more information, please check Curator Reference.