Why should you replace it? In my case the car wouldn't warm up at all. 7 miles on high and still not warm and this was only at 45 degrees F. I could feel some heat blowing but not enough to warm the joint up.

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How about the intake side

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New style Mehle cabin filter (sorry no pic) is all paper with foam around the exterior. No plastic but fits right in like the one with the plastic frame, seems to seal better but I am not on the inside looking around the stuff. I guess if careless you could mess it up easy but it went in pretty easy. Had a ton of stuff to vacuum out of the filter housing which reminded me of wanting to vacuum the cowl a lot more often.

While I was at it before the cold front I cleaned the windshield with a rag and lacquer thinner and then applied aquapel. I absolutely hate having to use wipers cause they suck. If the windshield is treated it should be a clear view where regular wipers in rain sucks.