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.