Interesting - learning styles can definitely vary among kids. For us even given infinite time I would probably not have stretched much longer on many days. I found too much truly new material at once could be overwhelming and I started to worry about mastery and retention. Also my son's focus and drive only last so long and I'm concerned that things stay fun so he keeps going long term. So I'll tend to err on the side of stopping a little early. Although I'm totally with you on the sections where he was reviewing it was very satisfying to plow through a huge section quickly.
