Joe
Tuberosa does not have to go dormant if you keep it warm enough. If it does keep it on the dry side but not too much. I think it will start going dormant in the 50s. I tend to have problems at this point with them, I have lost several due to dormancy. I would recommend that you try to keep it going. If you do loose branches new ones will start to sprout up. Keep it warm and let them grow.

thanks for the info,I 'll keep them going under lights for the winter. joe