After how many km should one change the pollen filter?

When, roughly, do one need to change the pollen filter on a K12 from 2004 (w air condition) that has gone 10 000 km? Note this is in km! I know it can vary due to where you have driven the car, but roughly, since I don't want to do the job if it's not near when to inspect and perhaps change.

I didn't even know I had a pollen filter. I started searching an answer for my problems with no air coming from one of the mid vents. It's the vent hole to right of the steering wheel/ left of the two vents in the middle where the radio is. I understand this has nothing to do with the pollen filter, but if I need to tear everything down, I might as well perhaps change the pollen filter.
10,000 Km (6200 miles) is not the distance that you generally require a pollen filter change unless you live in the part of the world that warrants it! how long in time has it been since the change? generally when servicing any parts of the car it is usually on mileage or time lapse since the last service.:unsure:
The filter has never been changed.

Just a thought, since I might need to open up the vent system to see what's blocking or hindering air from coming out from the left of the two middle vent holes, beside the steering wheel. Since the other one works okej, it can't be the pollen filter, as I assume that it would affect the whole system.