I've got several in pots, some have been going several years now. They stay on my balcony all winter, they have all come through fine, but I think you should protect them if you get severe frosts.
I seem to remember there are 2 sorts- broad leaved and slender leaves, one loses all its foliage overwinter and the other stays evergreen but can't remember which way round! They also like to be pot bound to flower - treat them mean, they love it! One of my most favourite plants.