Newton began his academic career in 1667. for how long was he a working scientist? was he a very productive scientist?

1667 + 29 = 1696.

Explanation:  29 years beauce in 1665 he spent two years in solitary academic pursuit.

During this period, he made significant advances in  calculus, worked on a revolutionary theory of the nature of light and color, developed early versions of his three laws of motion, and gained new insights into the nature of planetary motion.

In 1696 Newton left Cambridge to take a government position in London. Then his years of active scientific research were over when he died in 1727.

Yes he was a productive scientist.

scientific laws are the result of testing theories and proving them to be facts.