Putting the IQ debate aside, proponents suggest beyond 120 having additional IQ doesn't translate to any measurable advantage. Intelligence has a threshold like basketball. You only have to be tall enough. Beyond this level of IQ becomes relatively unimportant.
Lewis Terman's case study is probably the most comprehensive yet on IQ, you can read more here http://alumni.stanford.edu/get/page/mag ... e_id=40678
As for what IQ scores can predict about a person's future, Hastorf offers a middle-of-the road position: the tests are pretty good at identifying "school-bright" children, those likely to perform well in ordinary school settings, but "on the issue of what makes you school-bright, it's obviously a combination of variables -- your genetic constitution, your biological health, the motivation that your parents put into you, chance."
Though the Terman kids were handpicked for high IQ, the longitudinal results tell us little about the meaning of IQ, except for one study conducted by Terman's associate, Melita Oden. In 1968, she compared the 100 most successful and 100 least successful men in the group, defining success as holding jobs that required their intellectual gifts. The successes, predictably, included professors, scientists, doctors and lawyers. The non-successes included electronics technicians, police, carpenters and pool cleaners, plus a smattering of failed lawyers, doctors and academics. But here's the catch: the successes and non-successes barely differed in average IQ. The big differences turned out to be in confidence, persistence and early parental encouragement.
In other words, intelligence alone doesn't guarantee achievement. But then, you don't have to be a genius to figure that out.
I am intrigued, Einstein was rubbish at most subjects. He hated them, I suspect he would have failed most entrance exams as he wasn't "well rounded" as he cared about physics and maths only.