Are we teaching lectures at the ideal length?

I recently ran a poll on Twitter about the length of the lectures we are teaching, and what we find the ideal length. Of course, the ideal length for a lecture depends a lot on the topic – I wouldn’t be able to teach a laboratory class in a 50 min lecture. The classes I teach are 1h20 min, and it seems to be a good length of time for lectures. For exercises, however, it often feels short. On the other side of the spectrum sits Vrije Universiteit Brussel, where classes with exercises used to take 4 hours when I was a student. And of course, sometimes four hours would feel very long.

Here are the results of the poll and its wake: