Independent Reading for Narration in Year 2

SA(7) is reading quite well now. Ambleside Online's booklist for year two is still mostly too advanced for him to read on his own, and I read most of them aloud to him. However, I have given him two books this term that he reads independently, and then comes and narrates to me. These two books are Holling C. Holling's Tree in the Trail and The Burgess Animal Book for Children. The language in these books (particularly Burgess) is relatively simple.

I am still keeping the lessons where he does this very short at ten minutes, but I am hoping to stretch them to fifteen or even twenty minutes by the end of the year. He is doing extremely well. He actually does a better job of narrating these books than the ones I read aloud to him. This may partly be because they are easier books, but I suspect it is also partly that his learning style is more visual than auditory. There is also a little bit of excitement in the fact that he feels like he is telling me something I might not know (since it's not something I just read aloud to him...).

I have also tried having him listen to Librivox and read along for some of his more difficult readings (The Little Duke). I am not particularly happy with that option, as I often feel like I could read it so much better to him myself, even with the French pronunciations. He likes the novelty of the audiobook experience, though, so we do it for variety sometimes.

Because of the very short lessons, we are "falling behind" on the Burgess Animal Book for Children...we are just not keeping up with the Ambleside Online schedule for it. However, he is enjoying it so much, owning it, really (this is his book to read and narrate from), that I'm not eager to jump in and help him move through it faster by reading some of it aloud. So we'll just continue at a comfortable pace. No doubt we'll speed up a little before the year is through.

Fellow CM homeschoolers, how do you transition from reading aloud to independent reading for narration? Is it a gradual process for you, or do you begin all at once at a certain point? I assume the time a child is ready varies widely from child to child. I'd love to hear your experience.