I met a guy two weeks ago while on a Nikonians trek to AZ who has a 32 GB CF and a 32 GB SD backup card for every day he shoots. He must have had at least eight sets of those cards in a flex wrap case with see-thru pockets. Now that is a guy prepared for memory card failure!
He is a pro shooter and NPS member. I will not be following his example...I would have to rob a bank on my way to the next trek.