As with most plants growing from corm root structures, liatris routinely generates new corm structures as it uses up the energy and nutrients of the previous corm. So while an individual corm is not long-lived, it reproduces itself through offsets. The result of this is that a Liatris clump may begin to die off in the center as new stalks emerge from new corms. A Liatris clump can therefore live for many, many years, though it may become somewhat sparse as old corms die out. You can assist this process by digging up the entire clump every few years to divide the corms and replant them to maintain a vigorous colony.