You could combine Modules 1-3 into one year and either leave out the Bible portions (which I don’t recommend bc they are integral to history) or have a separate Bible time. However, I don’t think there is any magical rotation. 4 years is what classical trivium people do, but its rather arbitrary IMHO. In all of my schooling I NEVER went through all periods of history. In school we had 8th grade state history, 9th grade world geography (the most boring class in the history of mankind. I mean who needs to remember exports and GDP and other facts devoid of context.), 10th grade was economics and government (again textbook drivel), 11th grade was US history (made tolerable by a decent teacher, but still textbook boredom), 12th was world history (crammed in one year and utterly worthless).
At one point I stressed over how many times we would go through a history rotation. Should it be 2 or 3 or 4 or ??? Then I realized that no one on earth will ever know all there is to know and that even going through once would be more than I got in my school years. We’ve settled on using SCM’s 6-year rotation because it lets us linger as desired in a period. It isn’t rushed. It isn’t so crammed full that we can’t add other books of interest. It works for us.
Just my 2 cents.
Christie