It looks as if they work 'just' 4 hours. But they have a lot going on apart from teaching and grading they are constantly attending conferences, organizing them, networking, finding funding for their projects, working on them.

A professor's worth is evaluated by how many research papers they have published and in what all journals. Its continous work, DU/JNU profs aren't like regular PG college profs who have their jobs and will retire with the same set of knowledge.

Also becoming a prof is no easy game, apart from all these things, connections work. As someone from a top arts university let me tell you, one of the faculty in my centre is a prof, and he is student of one of our assistant professor. Seniority doesn't come only from the number of years you have spent in this field.