We are doing that this year, I just personally didn’t want to spend a year in each of the ancients, and I don’t think my kiddos did either. I think it’s pretty easy once you learn how to be more flexible with the lesson plans. For us, we also use substitute books if I can’t get the recommended books at the library, so then it’s easy to just make our own schedule with the books we have. I don’t know how young your children are, but I think when they are younger, American History (or whatever country you live in) and modern history is more important than the ancients, so we spend longer/more frequent rotations through them.