Ideally all the time; winter and summer. However, if you don’t want to do this then 30mins every 2 weeks will help to keep it in shape. This is needed to circulate the special oil that lubricates the system. Without using the a/c the main seal dries out and the gas is lost.
A/c works well with the car’s heating system, winter or summer. Many people find the a/c helps them, as it is filtered, dry and cool. It can also help keep children from overheating on long journeys.
Ideally, used regularly it should last 4-5 yrs. Eventually, sufficient gas will be lost for the system to be inefficient and stop cooling. When this happens what remains in the a/c
system is recovered and a full charge added. This is all done by weight, which is why a car cannot be ‘topped up.”
It means that moisture is removed from the air as it passes into the cabin of the car. This in turn “demists” the windows very efficiently and stops it reoccurring.
Yes, as the temperature of the incoming air is dependent upon how long it stays on the cold coils of the a/c evaporator, the slower the fan the longer the air is on the coils. The evaporator is a small radiator that is inside the car that the a/c system uses to transfer heat from the air. However, a slow fan speed means it takes longer to cool the cabin, therefore use a fast fan speed to initially cool the cabin or demist the windows then a lower speed to maintain cabin temperature or clear windows.