I like to use the analogy of going to the gym. If you go to the gym and your goal is, 'I want to look just like David Beckham,' then that drives you to do certain things. You may never look like Beckham, but it is a goal. Cities need the same thing. They need a vision and a plan for their ideal physique.
There are some designers who flash and burn - Courreges is an example of that. But he still marked fashion history. And I don't think that longevity is always a badge of honor. Modern brand management means that we are always celebrating birthdays, when what is exciting about fashion is innovation, not repetition.