Due to some mildew issues in past years (we are near the ocean) I keep the rooms controlled around 50-55% relative humidity and 60-70 °F with a big dehumidifier, and the central fan running 10-15 minutes per hour. We don’t have to run the a/c very often. No stale, damp air allowed, which is good for the clocks and watches too. And my throat and sinuses benefit too.