Depends what you call your originals, I don't really consider my on card images the originals (even though they really are), but rather the main copy on my computer the original. That being said, I typical don't format my cards, until after I've gone through and edit pictures, and either delivered photos to client, or uploaded them to to Flickr. This way I at least have decent quality edited jpeg backups.
I also typically use my cameras that have dual card slots for important stuff which reduces risk furthur. It is still quite possible I could format both cards thinking my images are safe on ym computer, but normally having to format the second triggers me to double check they are safe on my computer.
It would come down a lot to your shooting style, But i'd be unlikely to use more then 8-16gb a day shooting RAW while travelling, I'd also prefer having 2-4 large cards, then having to manage tonnes of small cards.