More than two or three "Retard" calls is a clue that the thrust was left up too long.
On a normal day in the A320 Airbus recommend you should close the T/L promptly at 30' and there should be no "RETARD" reminder. If you leave it too late the thrust starts to increase to maintain target speed in the flare, increasing the landing distance. On an autoland the RETARD call is an instruction and not a reminder - the A/THR will already have reduced thrust.