It is just a quick reminder that Google Analytics historical data retention time range will be changed to 26 months after 25/05/2018. It means any data before 26 months ago will be deleted after 25/5, which might bring negative impact on campaign optimization. Below are the steps to prevent it from being deleted.
1. Sign in to Google Analytics
2. Click Admin, and navigate to the property you want to edit
3. In the PROPERTY column, click Tracking Info > Data Retention
4. User-data retention: select the retention period you want (Do not automatically expire)
Please feel free to find more information in the following source Analytics Help
right now i'm checking my Google Analytics and on the top one message are shown which is given below
"We've recently launched new Data Retention controls that may affect your data starting May 25, 2018. Please contact your Account Administrator to have them review your settings."
I can't understand, even read guideline also but still not sure about Data Retention.