I do the card swap once a week to download my videos onto the computer. Like M8TJT said, once the cards have the same settings, you can swap all you want without formatting. Took me a few times to realize why my settings kept reverting back to what I had earlier. I would be using both card 1 and card 2 at setting A. I decide to make a change (setting B) while card 1 is in the camera. Then doing the swap to take card 1 in the house and installing card 2. Card 2 still had setting A on it and reset the camera to that setting. So now if I make any setting changes, I must remember to take card 2 in to be formatted on the computer to it doesn't over write setting B when inserted in the camera. Then setting B will be written to that blank card, making both cards have the same setting change.
Something I just noticed, I took my card holder back out to the car this morning on my way to work, but my cards are still plugged into my computer. Have three sets to check each week. The front and rear for one and two side cameras.