Do child prodigies' intellectual growth plateau?

[miragesyzygy]

For example, if someone entered an elite university at age 14 or 15, is it necessarily the case that that 15 year old is roughly an intellectual equal of an 18 year old freshman? What difference in intellectual capacity lies between a 15 year old and an 18 year old?

But my main question is whether the people who didn't enter elite universities at a precocious age are doomed to inferiority forever. If someone enters Harvard at 15, will s/he always be ahead of the curve of his classmates who entered at 18, such that, when the individual in question is 25, s/he will be as smart as or smarter than the people who entered at 18 are at 28?

I would think that even a regular Harvard student who entered at 18 eventually plateaus, so that she at 2X is roughly as smart as she will be at 2X +3, so that the person who entered at 15, at 25, will be roughly as smart as the regular graduate at 28, but also that same regular graduate at 31 or 34 or 59 (or whenever before senility kicks in, if it does).

However, the student who entered at 15 has already been shown to have developed positively aberrantly, and I don't have any scientific evidence (if such can be provided) for my belief that a Harvard graduate at 2X...roughly as smart as...2X +3, so I wanted to know what other molds the prodigy can break.

EDIT: I switched gender pronouns midway without noticing, but the context should make it evident whom I'm talking about.