Product review (5 stars): Saves a lot of cleaning time
I'm not really sure of the mineral content of Lake Michigan water, but one of these cartridges seems to last an entire 5-6 month humidifier season and possibly more.  I never get any white dust or any deposits at all, and the humidifier base stays cleaner than other humidifiers I've had that didn't have such a demineralization cartridge.  They are not cheap, but the time it saves you in cleaning up dust and the humidifier base seems to me to be worth the additional cost.