Have you checked the destination folder listed in Debut's options-output window? I leave it set to the default, then create a desktop shortcut for easy access.
If you are recording very large files, I would definitely recommend using mp4 output format, and a usb 3.0 external hard drive of 4TB (4000 GB) or more. (Costco - $150). Set the destination folder to a folder on the external drive. And, of course, use a UPS (uninterruptable power supply).
And you should set the options-record option to create a new recording every hour or less (you'll lose a few seconds each time a new recording starts.)