Assuming your air con is working then, in my opinion, a service is complete waste of your hard earned.

I'd never come across servicing of aircon systems until about 5 years ago when the retail motor trade were going through a lean patch and were seeking further avenues of income. Thus the threat of Legionnaires disease, Botulism and all manner of nasty ailments spread to the service reception desk in order to scare drivers into acceptance.

Manufacturers generally do not include it in the recommended service schedule as it would add to the Whole Life Cost, a figure that they are keen to minimise in their promotions to the fleet industry.

My recommendation would be to have the aircon system serviced as often as you would have a similar operation performed on your kitchen refrigerator or freezer. When it doesn't do what it should do.

Being a tech at a dealership, my advise is to firstly check to see whether there is any cold air coming from the vents?

If there isn't any noticeable change there is a chance your air con needs a regas.

It's a bit difficult to tell if your A/c is cold during the winter months as the ambient temp is so low outside.

best time to check is at around 21 degrees C and using a thermometer any will do, leave it (thermometer) some where out of direct sun light so it reaches ambient temp (outside temp) and then put your air con system on wait a few minutes and then poke the thermometer into the vent (be very careful not to drop it!) leave it for a minute or so and you should get a drop of about ten degrees. This is working correctly.

An 'air-con' service should consist of an air con regas and a pollen filter change (need to ask dealers what they define as an 'air con service' as some just regas and not bother with the pollen filter).

My advise is to change the pollen filter every year to 2 years definitely, and maybe a disinfectant spray on the evaporator as condensation occurs onthe metal matrix and can cause a bad smell (bacteria) which can lead to legionaries disease or other lung related issues.

Air con gases naturally leak from systems through seals over a period of time and air con becomes less cold, that is when it needs to be charged up. Otherwise leave it.