Cards are fairly reliable and durable, IMO, and right now, very, very cheap. 16GB CF 400x from both Sandisk and Lexar are under $50 right now, so I'd tend to go this way for your primary storage for a month on the road under less than ideal conditions.
In Sept. and Oct. I was on the road to the Cyclades in Greece. This trip I made without my MacBook, relying on shooting cards once, then backing them to a pair of Hyperdrives and then cherry picking to my iPad.
I shot about 16,000 pix, about 1,000/day. Whenever the card was totally filled, I pulled it, cherry picked a few on the iPad and then downloaded it on each of the iPad Hyperdrives before putting it in the filled card file. I took over 200GB of media cards on the last trip and had but two files glitch on me toward the end of a card. A write error, best I can figure. Nothing I couldn't handle and I didn't really need in the overall scheme.
The Hyperdrives worked well and I was able to download for more than a week on a single charge. I had a back-up AA battery pack thinking I'd need to use it, but the battery in the drive was plenty to last half the trip on each.
I bought just the Hyperdrive case and put my own SATA drives in them since I could choose the mechanism and already had another drive pulled from my Macbook. I've also considered going to SSDs for the Hyperdrives to make them more durable. For a wet environment, this wouldn't work unless you bagged them and put them in waterproof Pelican or similar cases. In this environment, I'd simply rely upon CF and SD cards and small hard/water proof cases, carrying enough to shoot for your trip.
After all, before digital, we simply brought enough film and our back-up was to shoot two cameras and keep the film separated or shipped occasionally from the field. With the price, speed, durability of CF cards, I'm about to leave the support behind and enjoy my evenings on the road like back in the good old days! It's getting closer every day!