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
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.