I did not get to fluency in Prague in five days, but I took my Czech to a new level. I am satisfied that this strategy worked for me, and satisfied with what I achieved by having a focus for a year, leading to a brief intense period of immersion. I will do it again, and again.
Ideally I would have continued to work on Czech after leaving Prague, but instead I took 5 weeks of while traveling in Spain, Portugal and going to Berlin. But I will continue to work on Czech and Russian, even as I get cracking on my next five days to fluency challenge,Korean.
But it looks like my wife and I are going to Mexico in the Spring so I may delay my Korean trip a little bit. We will see.