The filter wouldn't be catching anything at this point and would put a huge strain on the system, thus shortening its life - though I like your cheery outlook!

The funny thing about this story, as that my client (the homeowner) hired me because her tenant had made complaints about mold.  It was one of the dirtiest houses I've had the displeasure of seeing.  I asked the tenant if she had been changing the air intake filter on a regular basis.  She told me she had just changed it within the last couple of weeks.  I whipped out my screw driver, opened up the panel and that is what I found. 

I told her mold should be the least of her concerns given the state of the home.

Sometimes it pays to be blunt.

David-

I agree.  I see this stuff all the time - and worse!

I had a call once from a Realtor about "a little mold problem under the kitchen sink."  There were huge mushrooms growing (the reverse osmosis system had been leaking for a VERY long time.)  They were trying to say the leak was "new" so I had the mushrooms cultured and most took at least 6 months to produce fruiting bodies.  Hmmmm...

The entire subfloor of the kitchen and into the hallway was saturated and you could actually ring out the insulation in the crawlspace.  Uggghhh.