may not have seen much use during the winter, it still is a good idea to give it a change, especially for longevity of the system’s sake.
because the air conditioner’s air filter collects dust and debris when in use, it is a good idea to sweep and dust the house before changing the air filter to help get a lot of that stuff up and out. also, a good cleaning will greatly help out the quality of air in your house, as well as the quality of air that will be coming through the vents.
during the mild temperatures is a great time to have a professional look over your system. 