This is a big one. I sat in on a number of 400 level CS courses after I graduated, and a big factor was just having a scheduled place to be, and homework assignment due dates that forced the correct pace for learning. The pace also made it easy to start the work early, but not obsess if I hit a roadblock, since there was a lot of opportunity to ask questions leading up to the due date. I don’t think I’d have gotten through the same course work without the classroom lectures. Double bonus was the social aspect, talking to other students and regularly walking with the prof after class.