I have a black belt. how long will it take to get a black belt in other disciplines?

This question comes up once in a while at the dojo where I am. I too have a black belt, which took me five years of hard training. The thing is, different styles have different methods of grading their pupils. Some have "time periods" in which students must have held their current rank for "x" amount of months, or the instructor may only hold gradings every so many months. But on the other hand, just because you are a black belt in one style, doesn't necessarily mean you'll have an advantage in another style. You will have to learn all of their methods of combat, and in some cases it may clash with what you have learned, and it can be quite difficult doing what you have been taught not to do. If the instructor grades by skill, it will really depend on how fast you can absorb the new material. In Judo for instance however, you have to win competition fights to show you have learned to better yourself in combat. There are far too many variables to give a definitive answer to this question, but previous skill MAY help. Best of luck finding a new art!