Had a little trouble with this feature on Windows 10.
From what I can tell, setting 'Mount as Removable' allows 'Save Contents to Image' and 'Save contents to associated image every, min' to work.
Otherwise, there's an error like can't save file cause another process has a lock on it. You'll see this error when you highlight the drive and click 'Save disk contents to image' on the apps toolbar. I didn't see this error being logged to the event log.
yes... I have now been running for 2 days and the image has been saving fine every 60 minutes.
I have not tried the scenario of adding a file, rebooting, and seeing if file is still there after the drive has restored.