What?! You had icicles!? I've never seen them in NC, and now I'm in Utah this week I'm missing them!
I tried to get some photos of the ducks on a frozen Yates Mill Pond a couple weeks ago. I was up early, got all my gear together, walked out to the bridge and tried to take a picture. No CF card. GAH! I've done that so many times! Of course, I didn't have time to go home again to get the CF card. *sigh*
But I'm sure my photo would've been almost as good as yours
I keep a 32GB SD card in the second slot of my 5DIII. It never comes out of the camera. It is my backup. My normal setup is shooting RAW on 8GB CF cards in Slot 1, and large JPGs to the 32GB SD is slot 2. That way I can fill up many, many 8GB RAW cards and still have room to spare on the backup SD card. While the JPGs aren't as forgiving in post processing, they are intended to be my safety valve incase something goes wrong.
I intentionally leave the SD card in the camera at all times. In my normal workflow, the images get offloaded from the CF cards on to my PC and external backup drives. Then the next time I go out and shoot, I just reformat and start over.
Having this second card has saved my bacon a couple of times. Once I went out with only one CF card because I didn't expect t shoot that much. But I hung around longer that planned and filled up the CF card before what was one of the best sunsets of the year. In that case, I just pulled the full CF card out and switched the SD card over to capture RAW. I've also forgotten to load up a CF card once or twice and having that SD card ever present save the day.
The only time the SD card comes out is if there is something on it I need that I don't have on a CF card, then it goes right back in the camera.