Innovation Peak, when ?

According to Watts Humphrey in his work called "Managing for Innovation" the innovative peak for engineers and scientists occurs two times in a life time.
The first peak happens in the early twenties, which is not much of a surprise as its common knowledge, however there exist a common belief that once innovative skills decrease over the years which W. Humphrey seems to disprove.
It appears that the decrease over the years are less significant than most think. And as an encouraging thought for the seniors out there, it appears that a second and much later peak occurs in the mid- to late-50s. He claims directly that this double-peak occurs among all the groups of engineers and scientists and that the dip in between is not very significant.
He continues to argue that the late 30s and early 40s is a highly stressfull period, but once creative people pass this hurdle, they will continue their creative work for many years... he sums it by pointing to an all american icon, Edison, seeing that many of Edison's 1.100 inventions were produced later in his 84-year life.

Good news for us that intend to stay in the creative and innovative part of the software industry for many years.