First-time poster. Please bear with me.
I've had the "unfortunate" experience of training in styles, systems, and methods that don't utilize belt levels. You develop skill and spirit, not earn rank or certificates. You get better. That's it.
I've decided, however, to use belts not only so that my students have clear goals, but so I can glance at them and know what they have learned and how they should be able to perform at their given level.
My students can advance when they've reached certain degrees of technical knowledge, physical attribute development, and the like. Additionally, there are time requirements in the form of both total hours logged at their level AND minimum amount of months to have passed. That way, people canÂ’t go too fast, yet those who go slow (whether they be hard-learners or part-time students due to other obligations) can still participate at their own speed.
For example, Phase One students in my school must put in at least 25 hours over at least six months. With two class hours available per week for this level, they need come once a week to make their requirements. FYI: Phase Two students must come to two of the three available classes per week; Phase Three learners need to attend three of the four open classes each week.
When a newer student shows a great deal of skill, likely from previous training in a similar style, I look to see if senior students and assistant instructors agree that the newer student should be allowed to accelerate in rank testing.
When that happens, I take away the minimum months requirements and allow the newer student to pass as fast as one could possibly take the needed number of classes. For example, a Phase One student could in theory take two classes per week and reach their needed 25 hours within 3 months, not six.
Phase Three graduates have a minimum of 350 hours of classroom instruction under their belts, earned over at least 3 years; this is specifically designed to mirror the black belt level in many local schools of traditional styles, including the TKD I've also trained in.
That brings up the question of how many HOURS, not necessarily how many YEARS, you think it'd take to become black belt.
A couple more kernels of food for thought. One, while my students can gain black belts in a few years (a little more than 4 years usually bears this), its not until they've reached an approximated Phase Five, which takes on average 8-10 years, before they can start teaching their own classes.
Two, someone mentioned a Tang Soo Do school. The head instructor in one TSD studio I used to train tells students that it should take between 2-7 years to earn a black belt, with 4-5 years being the average.