The Artica v4.30.00000 Service Pack 209 allows you to define the statistics retention time.
By default, logs file are deleted from disk if their size exceed 100Mb and statistics max retention time is 5 days for a community edition and 365 days for an Enterprise Edition.
The section “Logs Center” / Retentions allows you to define the time to live of statistics and log files.
The first section defines retention of all statistics databases and especially DNS statistics in days.
The second section is focused on the log files and events: