G'day Jas,
I installed in our 80 a K&N 70 000k's ago, 2007.
More than happy with it, carry the cleaner and oil with me on trips.
09 drove through that huge dust storm that covered the whole Eastern part of the country, we were on our way to St George. 8 Hours of pulling a camper, some of that into a head wind full of dust.
The K&N did it's job, the air box was caked inside with dust, but beyond the filter on the inside it was as clean as.
Cleaned the filter, re oiled it and off we went, jobs done.
While I was cleaning it & Oiling it I had blokes standing around giving me their worldly expertise on the down side of the K&N filter.
For starters, my old 1hd-t doesn't rev it's ring out at over 9000+rpm all day like a race motor would in a dusty environment like an off road race track. My motor isn't pulled down and rebuilt after each race, because it doesn't get abused like a race motor does. My old girl is religiously serviced every 5000k's, oil + filter. K&N is inspected often & cleaned when it needs it.
Like you Jas, I'm a little skeptical about washing a fibrous material and reusing it, yeah I've read it is fine to do so, but something just says don't do it. It's not as if it is recommended to wash and reuse your dunny paper.
Anyway mate, that's my 2 Bob's worth on the matter.
A K&N works for me