It's said that if you ask two Korean immigration officers a question you'll get at least three different answers, so when I say that I was once told that I needed to be on two year F-2 visa before I could apply for an F-5, it's important to emphasise that this is not necessarily correct information, it's merely something I was told by an official - so it's a given that it might be inaccurate. In the same vein, I was also told that I might be interviewed the next time I reported in to my local immigration office, and my Korean skills could decide the difference between my getting a one or two year extension. This passive-aggressive language requirement is often also stated in connection with F-5 applications - despite the fact that there seems to be no legal basis for it, though personally I'm not opposed to the principle behind it. Anyway, perhaps in a nod to the highly subjective nature of the possible assessment, the immigration officer's parting words to us were "bring a baby with you next time, and it will be better".
They actually didn't say who the baby had to belong to, but subterfuge didn't appear to be required in the end because as things turned out the next time I entered their office it was with my eight-month pregnant wife, which while not quite the requested entirely separate person, seemed like a considerable down-payment towards that goal.
Baby or not, I was never convinced that I was going to face an inquisition, but I had to assume the worst and tried to study harder in preparation for it, although I can't honestly say that I was pleased with the results of my studies. But after months of it vaguely playing on my mind, there was no interview and the immigration officer told us that she could give me a one or two year extension but considering my wife's condition she'd make it two. And that, along with 20,000 won (around £11/$17) was the end of my visit. A year ago, my wife was preparing to apply for a one year visa extension in the UK, requiring a small mountain of supporting documentation, an interview in another city, and a non-refundable £800 fee. It can be tough getting clear answers from the Korean immigration system, but at least it isn't designed to hate people the way the British system is.
So barring any last-minute hitches, my next mandatory visit to my local immigration office won't be until 2012, by which time if I can't hold a fluent conversation with the officers there I'd probably be better off leaving Korea anyway.