Instruct: Classify Amazon reviews into positive or negative sentiment
Query: short life-span

Sure, it works just wonderfully when I first replace the filter, but it only lasts about 3 weeks, not 3 months. We use the humidifier all day and night in our very dry apartment which is only 500 square feet, and after even 1 week I start smelling the moldy smell. This is despite cleaning the tank and tray every 2 days (they recommend once a week) and turning the filter over every day. And you have to keep all the windows and doors closed, or it won't work at all. That makes for very stagnant air quality. Very disappointing.