Mises was in his prime from 1920-1934 while he was 39-53 years old. Three main areas in these years were certain people, his intellectual contributions, and other work.
Hayek, Machlup, Robbins, and Margit were chief among the people. Intellectually, he found socialism and interventionism to be inefficient. Mises refines his business cycle theory. He strengthens the case for free banking. Economics begins with choice. The theories are a priori. Mises worked on sociology, history, and epistemological problems of economics. He reported on the causes of the great depression in Austrian and wonders why the crisis lasts so long. He determines that it is interventionism that prolongs the crisis. He identified that union wage rates were obstacles to recovery.
Lecture 6 of 10 from The Life, Times, and Work of Ludwig von Mises, a George and Joele Eddy Seminar.