[pvaldes]

It depends in the issue, but IMAO on academia is not uncommon to spend about ten years studying a theme to became an expert on it. Plus university years. Plus school years. And there is a lot of inertia to not change your study subject.

Researchers in some parts of Europe spend around 25 years of their life (if I remember correctly the article) just trying to have a stable job, and this is criminal.

If you put an upper limit, the interval that remains is just too small to be profitable for the society and specially for the scientist. Nobody would want to do science.

Academics also spend a lot of time teaching, doing bureaucracy, and finding funds. So you have a highly trained people spending most of their expensive time not doing research.