Maint. schedule for MY2012:
It looks like they call for pollen filter @ 15K miles and 20K mile intervals thereafter. I like doing pollen filters at least annually...they can get pretty gross.
It looks like they want the air filter done at 55k miles. Probably an OK interval unless you operate the car in a dusty environment. (I did the air filter on my '11 A4 a couple weeks ago @ 31k miles and the filter still looked new - - it was spotless.) I've yet to do an air filter on the current A6 car, but the air filter on our C6 A6 was probably the most difficult air filter I've seen.
I often see installation instructions included with OE grade filters that would address both the air filter and the pollen filter. Unless you've done a ton of driving, I'd focus on freshening up the pollen filter. Buy two while you're at it!
(The cabin (pollen) filters are usually located just above where the front seat passenger's feet would be. Pretty easy to deal with.)