Will you have a third card so you can continue to use your dashcam during your vacation without overwriting the two cards that have your 12-hour drive recording?
If you have a laptop with a decent size hard drive, bring it so you can save the clips on to it for safe keeping, and you won't have to worry about having enough sd cards for storage.
If you have a laptop with a decent size hard drive, bring it so you can save the clips on to it for safe keeping, and you won't have to worry about having enough sd cards for storage.