Can a young student achieve testing "peak" by winter of his/her junior year?

In light of the pending changes to the SAT, I have been planning to have my sophomore daughter study for the current SAT over the summer (between sophomore and junior year) and take the SAT in October. She will then have the opportunity to re-take it as many as 3 more times, through January 2016.

HOWEVER, is it unfair to expect her to achieve her highest scores by that time? Is there something about age, maturity, development and high school education that says that she won’t likely be doing her best until late Junior year or early Senior year?

My daughter is a strong, self-motivated student. She took the SAT once before, in 7th grade, and achieved a score in the 1800s with minimal prep. She’s young, though, and will not turn 16 until mid December.

Regardless of how hard she studies or how mature she is for her age, is it doing a disservice to her to encourage her down a route where she will not be able to gain any improvements late in Junior year or during Senior year, without shifting to an entirely different test?