Unless your outside air unusally bad, a large filter bed of charcoal should last longer like 2-3 months. Also in green grass climates, a whole house dehumidifier could ideal to provide the base of air movement and humidity control.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"