Filters should generally be replaced every month when the system is running. Replace filters of the same kind and size as the original filter. If your filter is not disposable, follow the manufacturer's instructions for cleaning.
If you're using a high-density filter such as an electrostatic filter, check with Ragsdale Heating and Air, who can raise the external static pressure of your system. If the external static pressure exceeds the design criteria of your system, it can negatively impact the performance and life of your equipment.