A Debian user reports that PreserveJobHistory does not work for him:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=921741

I have confirmed this with

cupsctl PreserveJobHistory=30

and printing to a queue with cups-browsed stopped. The c and d files were removed immediately. The error_log shows (on four consecutive lines):

[Job 248] Removing from history
[Job 248] Unloading...
[Notifier] state=3
[Notifier] JobCompleted

(I did read #4732).

Regards,

Brian.