Tidelanders, when it comes to automobile maintenance, you base your vehicle's oil changes on miles driven. You should manage your HVAC system's filter changes the same way and base it on runtime. In fact, many new thermostats will track system runtime and prompt you to change the filter based on hours of operation. 

Restrictive air flow decreases operating efficiency by increasing system runtime and can reduce the life of the HVAC unit's blower motor. As for those "90-day" filters? We recommend you check them every 30 days. 

Even the nation's leading filtration manufacture, Filtrete, touts the importance of runtime and monitoring air flow with the introduction of their new smart air filters. 

Your HVAC system works hard to keep you comfortable. Reward it with a fresh, clean filter especially during extreme temperature events.