Murphy’s Law says that as soon as you travel more than 100 miles from a camera store, your camera’s chance of failure quintuples! This happened to me on a trip to Lake Tahoe with the Nikon D1. It happened to a friend of mine who took two EOS 1V film bodies to Iceland, both of which shattered their shutters the same day. And it happened twice to Arnold Crane with Leica R film bodies in Beijing, where 2 of 3 bodies failed from water (rain) and another one (separate trip) in San Francisco (bad mirror). Arnold reports switching back to Nikon as a result, but the truth is that any brand can fail, whether or not the camera is the top-of-the-line or not.
An acquaintance bought a brand-new Canon EOS 1Ds Mark II for a fall-color trip a few years ago. Slinging his tripod over his shoulder, he watched it plummet (along with the 100-400 zoom) 20 feet into shallow Maine seawater and rocks, shearing the lens off. Bad exposure on that shot.
Of course, you need to gauge the cost of the trip against the cost of redundant spares. But suppose you spend $10K on a once-in-a-lifetime trip to Africa or Antarctica or the place of your dreams. Or maybe it’s “only” an unusually special occasion for a loved one, but one that can never be repeated.
The point is to assume that a failure will occur sooner or later. This applies to camera bodies, batteries, lenses, chargers, computers, etc. Duplicating everything isn’t feasible, but at a minimum you should have twice the storage you think you need (in case the laptop or download device fails) and you should have two or more camera bodies and two or more lenses. Buy the cheapest body available, rent one, do something to make sure you aren’t left empty-handed.
For camera bodies, a nice usability bonus is not needing to switch lenses between one body. Lenses need not be identical, but more than one lens means you have something to shoot with. And this is one darn good reason to take at least one sturdy Zeiss ZF lens as a backup—complicated AF lenses with electronics do fail (and so do manual ones!).
Finally, for remote trips, you can “fail” too—so be sure to sign up for air ambulance service, which costs around $300 for the year, offering 1000X the protection. Doctors offices sometimes carry fliers for them.