How long can you take a living book/nature study only approach to science?

As I have been working through our plans (both for next year specifically, as well as more long term-big picture kind of stuff) I’m wondering if those of you who have successfully transitoned your kids into high school can share how long did you find using nature study + living books sufficient for science – and still be adequately prepared for high school level science?  At what point is it absolutely necessary to transition to a more rigorous formal curriculum (such as Apologia or something like that)?  Has anyone done nature study/living books all the way through 8th grade? 6th?  Or is it better to start using something more formally earlier?   I know some is probably just personal preference and how much of a “science” type the parent or child is…but I’m just wondering what the bottom line would be.  My main goals for elementary school level science are to develop a sense of interest and awareness in God’s world, develop the habit of careful observation, and be prepared to tackle more advanced science studies in high school (we aren’t sure if we will still be homeschooling at the high school level – I want my kids to be adequately prepared for what’s next” either way.)   Hope that makes sense!  Thanks for your insights.

Jen