History Note Revision Intervals?

So I've made notes of all of my history textbooks for my history exams, 2 AS 1 A2 (other unit was coursework)

I was wondering what the most effective length of time is between study/break intervals?

I've heard some people say 20m, some say 30m, some say 45 minuites and some say 1 hour.

I know that it depends on the individual. Lets say I'm of average intelligence with an average memory and average concentration.

Remember that history notes are names, dates, facts, figures, courses of action taken and, in my format are in sentences (per point).

Thanks