That is what I do. Update the car before flight, take to the airport. This way I have all new weather and TFR data. The I take the old home with me to start it all over for the next flight. Always having a backup with me.
After talking with Sandisk and them telling me that a 1-2% failure rate on SD cards is acceptable to them, I decided I wanted to reduce the odds by having two functional SD cards on me in the air. And Sandisk is the lowest, most guaranteed card.