I have a 1996 Acura Integra. The salesman at the dealership where I bought my car explained to me how to use the heater controls. He said, keeping the A/C on during the winter will give me plenty of heat and also helps my air conditioner last a long time. I have been doing this but I don't understand the benefits. I had hoped you could explain.
Salesmen are not always the best source of technical information.
Realistically, the only reason to have the A/C compressor engaged in cold weather is defogging/defrosting. Moisture condensates on the cool A/C evaporator under the dash and keeps your windshield clear, even while there is hot air coming out of the defrost ducts.
The amount of time the A/C is used for defrost during the winter is more than sufficient to circulate refrigerant oil through the system. So you don't have to worry about the longevity of the A/C compressor.
Let's follow the path of air through the system. It starts with the blower motor. The blower is pulling the air into the system, either from outside of the car or from inside the passenger compartment. This depends on what position you have placed the "recirculate" control. Next, air travels through the evaporator. This is the unit that cools the air (looks like a small radiator). On we go to the heater core, another little radiator, only this on is hot.
From there it all depends on where you select the air output. You may direct air out the defrost ducts (up top), A/C outlets (front and center), the heater ducts down below or sometimes a combination of two paths.
The air conditioning being on does dehumidify the incoming air. That's why many vehicles automatically engage the A/C compressor while in defrost mode, but turn it off when heat is selected. However, it also reduces fuel economy and increases wear and tear on the A/C compressor.