Since they got rid of the Lincoln memorial on the reverse of the penny and replaced it with an imitation of a state highway marker, now is the time to use the back of the penny to commemorate all of the counties. If they did 2 a week it wouldn't take that many years. It's the logical next step after doing the states on the back of the quarter.
Students at Washington and Lee University have found a use for the penny. They put pennies on the grave of Robert E. Lee’s horse Traveler. They put the Lincoln side face down, but put quarters and nickels face up to honor Washington and Jefferson. Supposed to bring the student luck, I think.