Aircon is one of those systems that stays serviceable better if it is used rather than not. As many on here know an unused aircon system is more likely to suffer from gas leaks and seized compressors, this is due to the lubricant in the gas not being circulated. The lubricant is reason enough to have the system serviced every 2 or 3 years and I mean serviced not just regassed.
Yes that costs money but so does the rest of the car to run and the aircon has very obvious advantages throughout the year. As for getting rid of the smelly bacteria, you can do that yourself with gas canisters that are available.
Vic.