Black belt just represents a certain level of skill and knowledge
It isn't an absolute but differs amongst organisations
One org it might represent a certain level of fighting skills others demand understanding of the techniques used
again other just that you can perform a specific part of the curriculum
As stated before most will go upto 5th degree BB for this, anything beyond is awarded for other things but not just for age or politics ( except for McDojo Styles) most of the time you are awarded those for what you do for the styles/arts
For instance one of my teachers travels all over Europe and charges very moderately for it, therefore he has been awarded 8th debree BB ( I believe between 5th and 8th was a total of around 20 years)
Another, Jon Blumming, who introduced Kyokushin Karate in Europe was awarde 6th degree bb by Oyama but eventually was awarded 10th by the highest graded students ( 6th and higher) in the same way as Oyama was awarded 10th
To conclude BBs are steps, in fact dan means just that, step
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