In December I discussed a major change in the TimerJobHistory table maintenance introduced in November 2017 CU.
Historically SharePoint 2013 preserved the timerjob history for all timerjobs which ran in the last 7 days. Starting with November 2017 CU for SharePoint 2013 (build 15.0.4981.1002), the maintenance of the [dbo].[TimerJobHistory] table has been updated in a way that it will never keep more than 10,000 job records.
Several customers provided feedback to us that the new maintenance strategy caused problems in larger farms with long running timerjobs. For these customers the hard coded number of 10,000 records prevented them from seeing if the long running timerjobs succeeded or not, as they were purged from the table at the moment the timerjob finished.
To solve this problem April 2018 CU partially reverted the change in the TimerJobHistory table maintenance back to time based trimming rather than trimming on a fixed number of records. Starting with April 2018 CU the timerjob history for all timerjobs is preserved for 3 days. This is in line to the maintenance strategy used on SharePoint Server 2016.
This also means that it is again important that the Delete Job History job runs successful on a regular basis.