I have several tropical hbiscus that I keep in containers as I live in Southern Ohio so I can bring them in for the winter months. They seem to do very well, but as they keep getting bigger, I keep repotting them and the are getting quite heavy and difficult to bring in. Should I prune back the roots periodically to keep them contained or should I consider letting them die out? Should I cut them way back now that I have brought them in for the winter? And if so how far should I cut them without harming them.