By default, on the Plesk server, web and traffic statistics are stored for 3 months.
How to increase this storage period?
Go to Service Plans > select a plan > Logs & Statistics tab.
Specify the number of months required for the parameter Retain web and traffic statistics.
Click Update & Sync to apply the changes.
Note: Service plan changes will be applied to the newly created subscriptions. For existing subscriptions refer to the command-line solution.