Using it >3 years. Previously we had a 3-4 month exchange interval. After moving, we need to exchange every 2 month. There seems to be a lot more stuff in the outdoor air, but the indoor air stays clean as well as the ducts.
Though my heat pump installer claimed this filter was "a compressor killer," I've been using this filter in my heat pump for a year and half and my compressor isn't dead yet. In fact, it hasn't even shown any signs of duress.