Got this email today from Google.
You can set controls for how long they retain certain data due to upcoming GDPR rules.
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Dear Google Analytics Administrator,
Over the past year we've shared how we are preparing to meet the requirements of the GDPR, the new data protection law coming into force on May 25, 2018. Today we are sharing more about important product changes that may impact your Google Analytics data, and other updates in preparation for the GDPR. This e-mail requires your attention and action even if your users are not based in the European Economic Area (EEA).
Product Updates
Today we introduced granular data retention controls that allow you to manage how long your user and event data is held on our servers. Starting May 25, 2018, user and event data will be retained according to these settings; Google Analytics will automatically delete user and event data that is older than the retention period you select. Note that these settings will not affect reports based on aggregated data.
Action: Please review these data retention settings and modify as needed.
Before May 25, we will also introduce a new user deletion tool that allows you to manage the deletion of all data associated with an individual user (e.g. site visitor) from your Google Analytics and/or Analytics 360 properties.