I write books. Not having a hard copy of your manuscript is a not good idea, since A)many publishers will only accept printed manuscripts, and B) just because you've backed up your work from the computer that just blue screened doesn't mean something won't happen to your backup (speaking from experience. 1 file saved to two computers an a flash drive. Laptop needed to be redone, computer got the 404 virus and the flash drive is probably in Bermuda by now.)