[Bugzilla user: bgo@osimis.io]
[Bugzilla date: 2021-01-19T10:11:04+00:00]

After some tests where physical installations of Windows 10 behave in the same way (i.e. forcefully killing Orthanc after 5 seconds) and more research, the conclusion is the following :

"Windows normally waits 5 seconds for background services to clean up and close when you tell your computer to shut down."

This delay can be customized through the WaitToKillServiceTimeout registry value.

"Some applications may change this value when you install them, giving their background services extra time to clean up."

(Note: Orthanc does NOT modify this value, neither at installation time or at runtime!)

If you notice that Orthanc (or any service, for that matter) is forcefully killed before being properly shut down (you can check this by performing a shutdown and checking whether the last log line "Orthanc is stopped" can be found in the log after restart), you can change this delay by modifying the 

WaitToKillServiceTimeout value in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control registry key.

The values are expressed in milliseconds.

"Double-click the WaitToKillServiceTimeout value and enter a number of milliseconds. The default is 5000 milliseconds, or 5 seconds. To set it to 20 seconds, you’d enter “20000”."


Info has been taken here: https://www.howtogeek.com/282062/control-how-long-windows-waits-before-killing-apps-at-shutdown/