NOTE: You are looking at documentation for an older release. For the latest information, see the current release documentation.
This functionality is experimental and may be changed or removed completely in a future release. Elastic will take a best effort approach to fix any issues, but experimental features are not subject to the support SLA of official GA features.
Keeping historical data around for analysis is extremely useful but often avoided due to the financial cost of archiving massive amounts of data. Retention periods are thus driven by financial realities rather than by the usefulness of extensive historical data.
The Rollup feature in X-Pack provides a means to summarize and store historical data so that it can still be used for analysis, but at a fraction of the storage cost of raw data.