There is an option that is responsible for the retention of the tasks themselves and the exported data:
By default, deletion is set to 7 days. After seven days, the task and the csv file are deleted:
Aug 16 23:00:00 host kibana[1695088]: CSV expiry date: 7
Aug 16 23:00:00 host kibana[1695088]: CSV Export Task is expired. Deleting this task and csv file Report_1660032000440.csv
Aug 16 23:00:00 host kibana[1695088]: Task Deleted.. Now deleting file..