This depends on how frequently you use your AC and how old it is. New units are usually stronger and will not suffer damage even if maintenance is delayed. However, for older units with roughened parts, maintenance plays an important role in keeping the unit running. However; generally, you should have your air conditioner serviced twice every year. It's best to do so right before the seasons change, once in fall and once in spring. Moreover, you should also clean the filters periodically and check the coils and fins for any clogging. Doing so is a good way to keep your AC in top shape and for safety as well.