I am wondering when my search artifacts/shown results will be deleted.
Default ttl for ad-hoc searches is 10min. I would expect the results of my opened & completed search to disappear after this time. Currently they don't and the expiration time is updated every time I refresh the jobs manager.
Yes, you are correct default ttl for ad-hoc search is 10min but if job is actively viewed in Splunk UI then status.csv file changes mod-time continuously and due to that in Job Manager expire time increase at every time when you refresh job manager & job will not delete from dispatch directory.
ttl = <integer>
* How long, in seconds, the search artifacts should be stored on disk after
the job completes. The ttl is computed relative to the modtime of the
status.csv file of the job, if the file exists, or the modtime of the
artifact directory for the search job.
* If a job is being actively viewed in the Splunk UI then the modtime of
the status.csv file is constantly updated such that the reaper does not
remove the job from underneath.
* Default: 600 (10 minutes)