Many thanks for the lovely response, TropFrog. My heart heard you loud and clear.
You touched on a subject that I was wondering about: watering. I should water only when temps get above 0 degrees Celsius I would imagine.  The frequency of watering is a question in my mind.  Also, my son's description leads me to believe that the Procumbens was hastily repotted when he bought it. Over the months of watering, many of the small rootlets have become exposed. I can't imagine that's good. As a stopgap for the winter, I have some moss from our mountains that I've put over the rootlets, leaving the outer soil exposed to allow some evaporation. Is that okay? I hope that we have a heavy snow year, so I can bury this little guy.   .  I'm signing up for a beginner course now. 

covering the exposed roots is ok, but the moss does not look good. I think I would top dress with soil rather than moss, watering is done when it is needed even if it is below freezing. Water when the soil is almost dry. in the winter with the ambient temperature low and low light levels the plant will not dry out very quick, Depending on where you have it it might be once a week, or longer. The main thing is to check regularly It will not hurt is it does get dry at this time of year as it is not metabolising much, 

We may have different ideas of what frozen means based on location. Where I am it is just not possible to water when it is frozen. The water cannot penetrate the solid block of soil and just runs out the side of the pots.