I think you may have misunderstood what the previous owner was telling you. You shouldn't throw out the plant that has bloomed, but instead, as this part of the plant develops pups,(offshoots from the base), the part that flowered will usually go into a slow decline, and after 2 or 3 years this part with the old flower can be cut off, and the now larger pups will fill in to take its place. If you do decide to dig up the old plant and divide/separate the pups, wait until they are at least 1/3 to 1/2(better) the size of the mother, to replant as new plants.