Once a year is a good time to protect your investment, your Heating and Air Condition unit. Property owners may leave it up to the tenants to change filters, but do you want to trust someone else with an expensive system? Probably not. Miris Properties recommends calling in the heat and company to give the once-over to the unit, this way you have peace of mind that the unit is not overworking itself from dirty filters, or the condenser is not working properly. See the link below.