Product review (4 stars): Nine month replacement cycle has been my experience.
LG typically recommends this filter be replaced every six months. I seem to get nine months out of these filters and our city water is pretty hard so I replace it every nine months. Generally, you will want to replace the filter when the water flow slows some or becomes erratic. The only thing that is a minor nuisance is having to run about 2.5 gallons of water through it after installation and before you drink water from it.