Product review (3 stars): Works well, but only lasted 2.5 weeks
I didn't use the humidifier for about four years, and then finally got got around to buying a this filter so I could use it again.  I was initially very happy with it.  I thought that the Amazon.com review that said it needed to be replaced every 4-8 weeks depending on water quality was probably setting people up so that when it lasted a few months, they would be happy it lasted so long!  Unfortunately, this couldn't be further from the truth.  This filter lasted only 2.5 weeks.  I received it December 15, and by January 1 I noticed the water tanks weren't emptying much anymore, and the humidity had dropped down significantly in the house.  I realize that we just probably have very hard water in Phoenix, but I doubt it's much better most places, so saying it will last 4-8 weeks is definitely misleading.  At $15 for this filter, that works out to almost a dollar a day.