Product review (3 stars): Generally I replace all filters including the water filter every six months as recommended. However
When I've purchased these in the past they have come with an indicator strip. The indicator strip lets you know at a glance when the filter needs to be replaced. Generally I replace all filters including the water filter every six months as recommended. However, depending on the time of the year they may need to be replaced a little more often.

Next time I'll purchase a filter that comes equipped with the indicator.