I decided not to use my USB thumb drive to create automatic backups for writing. I settled for my old system, well a slightly modified one. By copying my entire project and locating them to USB thumb drive.
On a USB thumb drive, I created a folder, Scrivener Project Bin Holder. On that folder. I created two folders. Folder I and Folder II. I popped my scrivener project in there. And will do so again in separate folder. A hell lot easier and faster than copying and replacing the entire project.
You would have to be damn careful in what you do. Especially when deleting a folder.
However I may decided to go with drop box. But sometimes internet can go out unexpectedly.