Basically, when a northern drosera or ping. Barry advised repotting hibernacs in new soil. I should repot them now or in March sometime. These CP produce only one true root which withers when the plant is very small.
All later roots are adventitious, being produced from the plant's stem.
When they regress to a hibernaculum all the roots and the old stem dies. I repot my plants when they go dormant. Hibernacula are also great ways to ship these plants. On the other hand, I go to great lengths to avoid disturbing CP which go dormant underground, like the S.African Drosera and Byblis gigantea. And I don't know what to do with my wintering D. arcturi.