For those of us who still have the system running, you have the option of leaving the cell in place and turning off power (or setting output to zero) so that it doesn't try to produce FC in cold water. Or you can remove the cell in its entirety and replacing with a dummy cell. In cold water, simply add liquid chlorine as needed to maintain the proper FC level. The chlorine should last much longer in these cold temps. The salt in the water doesn't go anywhere. If you elect to use tablets, be very careful how many you use because each tablet increases your CYA level. As the CYA increases, you are forced to increase the FC level per the
FC/CYA Levels. Check your heater owners manual, but most heaters warn you about using it once the water temp fall below a certain temp (i.e. 6o degrees) as it can cause damage.
In our pool, once the water gets too cold for the SWG, I just add liquid chlorine once a week or so. Easy stuff.