There is another parameter we should consider here :

ShutdownTimeout

 Number of seconds Caché should wait for shutdown to complete normally before timing out and forcing a shutdown. The default is 300 seconds (5 minutes). The range is 0 to a maximum of 231–1 seconds.
 
That means if there is a user process (or a background job !) that is not stopping immediately, Caché will by default wait 5 minutes before starting the system shutdown.
The time in 'WaitToKillServiceTimeout' shold be at least 'ShutdownTimeout', plus the max. time to really shut down Caché.
 
Right?