There is no maximum , all gradings are upon invitation including Shodan grade and under no circumstances is a student to ask when or for a grading.
This is for the Chief Instructor (Sensei) to decide and those that will be grading will be informed .
These grades will be taken at a minimum of 3 months regular training up to Purple belt to which this then extends to 6.
Novice white belt
Red belt 9th Kyu
Orange belt 8th Kyu
Yellow belt 7th Kyu
Green belt 6th Kyu
Purple belt 5th Kyu
Purple belt 4th Kyu + 1 stripe
Brown belt 3rd Kyu
Brown belt 2nd Kyu + 1 stripe
Brown belt 1st Kyu + 2 stripes
From 1st Kyu brown
6 months to 12 months depending for
Black belt 1st Dan (Shodan) - minimum time on regular attendance 3 years,
but not under 3 years and maybe longer depending on the student/s concerned.