I pulled mine out of their pots and trimmed them back hard, including the roots, then jammed them tight into a long trough filled with compost. I kept them in a corner of the conservatory and pretty much forgot about them apart from a brief watering and removing any flowers when I noticed them through the winter.
In spring I teased them out and replanted them into fresh pots for the summer.
They've had the same treatment for a few years and seem to do very well on it.
I'd hate to throw them away in autumn.
Sand