Welcome to the list Paul; This is my first time responding to a question, so let's see if I can do this reply thing right. Today I got a flyer from dampp-chaser mentioning a solution they just started selling which treats the humidifier water. It's a bacteriostatic, which (they claim) will lengthen the life of the pads. If you're using high-mineral water, changing to distilled water should help too.
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