My question to you guys is: how much "backup" or redundant photo gear do you carry with you when on an extended trip that's important to you to shoot pictures? What are the most important pieces of back-up gear to have, in your opinion? What's most vulnerable to failure?
I've happened to be on the same trip with a few professionals (e.g., Cathy Church, Tim Rock, others) who had at least two complete identical set-ups with them. Housing, camera, strobes, cords, not sure about redundant lenses or ports. This struck me as extreme, until last week...
The context for my question is that: last week in Bimini Bahamas, I had my first true housing malfunction (not that it really matters - an old-school Canon 5D in the Sea & Sea housing). Water leaked into the finder of the housing. Let me be clear - not actually through the o-ring that seals the finder into the back of the housing, but actually through the finder itself. When I examined it closely, there was a "ding" on one side of the finder which I believe had impaired the seal of the glass on the outside of the finder, and made it no longer pressure proof and allowed water to slip in. I was p***ed because I'd spent a bunch of money to go to Bimini, with the goal of shooting wild dolphins, and didn't have a workable photo setup, and no real way to remedy the situation. I actually figured out something of DIY workaround but it was far from ideal.
So the question occurred to me - given enough money to buy the equipment and to ship it with you, a good remedy is to carry a back-up. Spare parts like o-rings, plus a redundant housing, camera, sync cords, maybe even an extra strobe all seem obvious to ensure that you can shoot. But how far do you go with this - e.g., lenses themselves, lens ports? It is conceivable you could lose a port if you or the deck hand drops the thing on the port and cracks it. If you only have 1 dome port and you need to shoot wide angle, then your photography is done even if you have a spare housing. Similarly, if you flood one housing and damage your wide angle lens, you're done shooting even if you have a spare housing and camera!
Or alternatively, are failures of some things conceivable but so unlikely that the expense to mitigate it just isn't worth it?
One could go crazy (and maybe bankrupt) thinking about scenarios and carrying the backups necessary to mitigate them - so would love to get a sense of what you all think about this and what if anything you actually do about it in practice.