If that is the case for you, you can possibly stretch it to many weeks, but even if your AC filter does not look dirty after many weeks, you should still change it.
Whether you are looking to save money, or are interested in helping to preserve the planet, or even having a smaller carbon footprint, it makes a lot of sense to look for ways to save energy, including tips about saving on your air conditioning bill. What are some of the things you can do to lower your cooling or heating bill? If it is air conditioning, one good thing you can do is begin outside. That is, plant some trees or bushes that will supply shade. Having shade keeps your AC from having to start with a temperature that is way too high. Another thing to do is to have curtains or blinds in your windows, and personally I love to use insulated curtains, otherwise known as blackout drapes, because they entirely keep out the sun and the light. I know for sure that my AC does not have to work so strenuously when I have the blackout curtains closed. Another thing to do is to make sure that you change the AC air filter on a proper basis. Personally, I have a pet and I prefer to change my AC filters every week. Other people do not find that their AC filter is at all dirty after a week. If that is the case for you, you can possibly stretch it to many weeks, but even if your AC filter does not look dirty after many weeks, you should still change it. Another thing to do to save on your air conditioning plus have your beach house be more efficient is to use ceiling fans to your advantage. I have never had a home without ceiling fans down here in the southeast, plus I never will. Sitting under a ceiling fan makes you feel much cooler even though the temperature is not any lower than it is without the fan. This means you can have your control unit set a few degrees higher and still be just as comfortable.