Product review (4 stars): Works best without Humidifier Helper!
We were using Humidifier Helper and were going through one of these filters every 2 weeks.  Then we learned that the product actually shortens the life of the filters.  Now, just left alone, our filters last 3 to 4 weeks, set on the highest setting.  We order 5 at a time at this great price.  We use a few drops of tea tree oil in the water instead of humidifier helper if an odor develops.  It can buy us a few more days of use.