I take Ji Do Kwan TKD from a 70 yr. old instructor at a local YMCA. Our system of rank is yellow, green, blue, red (3 gups) and black. I have been studying about a year and a half and have reached blue and am getting ready to test for red. We have a minimum rule of 3 month between the gup tests, so would be six month minimum for black after attaining red, but I am yet to hear of anyone doing that in under a year. We have a pretty small class and I love it that way, but there is never any pressure for promotions. When you feel ready, you approach the master and ask when you can test (date wise). If he thinks you aren't ready he'll usually tell you. All of us in the adult class are older as well, I'm the youngest at 28. Some of the guys have taken 7 yrs + to reach black, and I have the utmost respect for that. Now in the junior class which I also attend, the kids tend to move up a little faster and the GrandMaster who presides over it tends to be a little more money driven which is sad. Hate to hear about schools being run that way, but I guess it all comes down to how you feel about it. I agree that everyone should feel that they have earned their rank and be comfortable with the requirements before advancing.