For those with a lack of imagination:
Check the date of manufacture... They were only installed about a year ago, I would say.
Only thing is...I have never come across an air filter that was directional! I didn't take note which way around they go!
I'm guessing air flow is in a 'downward' direction? Cause otherwise all the crap would fall down into the fan. This way the crap just sits on the filter medium, until your car turns upside down.
Anyway, 2x new filters were purchased when I got everything for the 120,000km service, so in they went.