When the temperatures is in the single digits, you don't think about your vehicle air conditioning system. But your air conditioning system is filled with parts that were meant to move. As with our bodies, if we stop moving for a while muscles start aching, we lose circulation. The same is true for your car. If you don't use your air conditioner for a few months, some components (such as the A/C compressor clutch) may become seized. It's a good idea to get that liquid flowing every now and again and keep those air conditioning components lubricated.
Also, bacteria and mold tend to build up in a system that is not regularly used. Ever turn on your A/C after not using it for a while and notice a bad odor? This winter, as part of maintenance, use your car's air conditioning regularly avoid potential repair costs for your air conditioning system. Hint: The same is true for 4WD. Be sure to engage your system regularly in the non-winter months.