would suggest that as you load the queue, you save as a session or job at regular intervals in case something goes wrong.
I was about to add.....
The beautiful part of Qimage is that it will allow you to load the images into the queue, from various folders at the same time.
Simply load the images from one folder and when that is done, change folders and add those images.
You can also create an Album with the 660 images to keep them together
Fred