I think you would see less advancement, not more.
First of all, fewer geniuses would be born (or raised/educated/self-made). The rate might be better than half, but not by that much.
Second, scientific paradigm shifts would overtake the aging scientists.
After 50-100 years developing in a certain paradigm (i.e. classical Newtonian physics), the bulk of scientists would not accept a shift anymore. This would hold the geniuses, and their work, back. Quantum mechanics was not adopted quickly or easily in our world, and it would've been much harder if the authoritative scientists had been older and more conservative.
Third, education counts for a lot. Each generation after Einstein, Bohr and friends got a much better start in Quantum theory, learning the latest theories in their prime learning age, enabling them to build on that. New paradigms would develop much slower with fewer students starting out fresh each year.
The combination of these factors would slow down scientific advancement seriously.
Note: This answer concerns our current level of advancement, where the leading edge of science and technology features large teams of scientists, engineers, and rapidly changing computer technology. An individual could spend 50 years perfecting a theory, only to emerge and find that some computer had proved it 25 years earlier by simply brute forcing the math.
I don't want to disparage the value of experience or years of diligent work, but when it turns into numbers, half the smart people living twice as long is a bad fit for modern science.
In Newton's age, and even Einstein's, advancement would probably have been quicker with longer lifespans, but that would only have led to the current situation a bit sooner.