Is the 3 months interval a regional thing, or based on the heat exchanger? Mine have 1 year intervals, and with a subscription for filters it is easy to remember to change the filters
>Is the 3 months interval a regional thing, or based on the heat exchanger?
both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.
