I read an SAE report a few years ago comparing oil bath wicking filters to some popular pleated paper and oiled gauze element filters. The oil bath was superior on all counts. VW knew what they were doing. It lasts forever and maintainence isn't really all that involved.

I had to wash the filter element on the '70. I sat the top part with the horsehair in a 5 gallon bucket of kerosene for an hour. As it became evident I'd go through kerosene forever, I went to TSP and very hot water. I went through 3 water changes then finished back in the kerosene. It was AMAZING what came off the horse hair, and scary. But when I was finished the hair appeared brand new and clean as a whistle. After the last water wash I hooked a compact hair drier into the outlet with duct tape and let it blow dry for a good half hour. The whole thing was toasty warm with no moisture left. Then I dipped it once into kerosene, dried it, then reassembled with a cleaned bottom half and new oil.

Has your filter had regular maintainence its entire life? And, just what did VW figure its life was? I'm quite happy with the result and feel much better about what the truck now sucks its air though.