For years, I’ve been hearing this wonderful argument: don’t put all your eggs in one basket; it’s better to have several smaller memory cards than one large one, so that if one fails, you’ve only lost a portion of your prized photographs, instead of all of them.

Seems to make sense, no? Distribution and redundancy are the core of safe computing, so we take this argument without question, spending extra to get four 512MB cards, even if the best bang for our collective buck is at 2GB. Yet do we ever stop to think that the entire concept is flawed?

The multi-card proponents convince us that all things equal (reliability and failure rates), four 512MB cards is the safer option.

But hold on a second there. Are the extra cards going for live, RAID-style backups? Are we afforded the advantage that while we sacrifice the space of one card, if any one card fails, no data is lost (RAID 5)? No. We have nothing. Until you get your pictures copied to your computer, there is only one copy in existence, and your work is in danger, either way. Your camera isn’t going to mirror your data for you. Maybe your fancy $3000 Canon EOS-1D Mark II does, but for us mortals, such extravagance cannot be afforded.

Remember that everything is equal, and we’ve just reached the beautiful world of digital permanence by splitting our eggs into four baskets? Billy’s 8th birthday will not be lost, because you had to spread the shots across four cards. If one fails, all is well, because you still have great shots on three other cards, right?

But it is that if that is important. Have you noticed that when you have multiples of something, you’re more likely to have one fail? In a family with three computers, one is constantly on the fritz. With five school-aged children, one is always sick. And with four memory cards, you’re four times as likely to have one short-circuit. The question is, do you want to lose a day of photos every two years, or an evening of photos every six months?

Our friend Murphy says that you will be losing the photos of Billy blowing out the candles, rather than the guests or the clean-up party. You’re going to lose digital photos occasionally, and the multi-card philosophy does nothing to prevent nor reduce this.

Someone is going to protest: “Richard, all memory cards are not the same. Some are more reliable than others; you cannot pretend they are all equal. Plus, you are more likely to have one memory card fail under intensive use, than to have one of four fail under intermittent use.” For them, I want to take this out of the realm of theory, and into the realm of practice.

How often does a door spontaneously fall of its hinges? It doesn’t; it fails when you open it. I have a Canon Rebel XTi, and it relies on a flimsy plastic hinge to stay attached to the camera. When the door is open, the camera magically does not work at all. This is one part I don’t want breaking in the middle of my adventure at the Grand Canyon (no, I’m not going to the Grand Canyon, this is an example). And when is it going to fail? When I open it in the dry, sweltering sun to swap cards, of course!

Memory cards and readers are usually rated for 10,000 insertion/removal cycles. We cannot assume that they’ll last this long; every time you swap, it’s wear and tear on the camera and cards, and with something as important as our photos, we want to avoid as much risk as possible.

Technicalities aside, trading out tiny, expensive, static-sensitive, photo-filled memory cards in the field is just bad practice. No matter how careful I am, I’m ten times more likely to drop my postage-stamp SD card in the grass at the park, or trip and have it fly into the river, than it is to fail on its own accord. Plus, you’ll miss great photos by having to switch memory cards. It doesn’t matter how well you schedule it—you’ll be clicking away, and the Kodak moment will pop up just as your camera flashes “card full.” It happens to me; I don’t even keep half the photos, but there isn’t time to delete on the spot. You can’t be ready for anything if you have no space.

You should have two memory cards, so that when one fails, you can order a cheap one online (with caution, of course), without your camera being completely useless for a week. Beyond two, there are no advantages.