Product review (5 stars): Helping get another season out of humidifier
Since the motor on my humidifier still works, all I had to do was run vinegar through it twice and replace the filter.  It's operating good as new, at least until it doesn't.

The filter is important as it reduces the really fine white dust just as advertised.  There's no way to look at the old used filter to know it should be replaced, but there's no way one of these can be used for two seasons.