It is true that if you leave a nest it will eventually die out naturally. The wasp nest actually starts to shut down in August, this is when grub production ceases. The last batch of grubs are the Queens and Drone wasps (these are the only fertile forms of wasps, the Queens being the females and the Drones the males, the majority of the population of a wasp nest are the workers who are all sterile females). These Queen and Drone wasps mate with Queens and Drones from different nests. Once these Queens and Drones have been reared then the workers do not have to collect food for the grubs, this affects their diet and behaviour. The food they collect for grubs is a protein meat diet consisting of caterpillars, grubs, flies and other insects which are mashed into a paste then fed to the grubs. In exchange the grubs produce a sweet substance which the workers like, this encourages the worker wasps to feed the grubs. This process ends once the Queen and Drone grubs are mature. Worker wasps now start feeding directly on sweet substances. This change of diet corresponds with the fruit season. Wasps feed on ripening fruit, get drunk and bold and more aggressive.People are more likely to be stung by wasps in the Autumn than at any other time. The other two main issue with wasps in October and November are light and temperature. Wasps are attracted to light and as the days get shorter artificial light becomes a big attractant which brings them into close contact with people. Lower temperatures make the wasps dozy and liable to crawl into areas where they can sting people.
So, is it worth treating a wasps nest in October – yes, because not only do you reduce the risk of getting stung you also reduce the risk of having another wasp nest(s) the following year.