I use 4 - 5 hours a day during night sleeping. 3 years ady no service, still cold and windy. Every few months did clear my filter.
Asked aircon ppl, they say 6 months - 1 year...
Asked some other ppl (dont want say out who are they), they say as long as aircond cold and no issue, no need service, just rmb to clean filter. They say thier aircond use 10 years only seviced few times, still strong n solid.