It is useful when they are doing too big a bug, but beware that at more than two or three hours, listening (unless the teacher uses methods I do not know) is not beneficial; if I am at least minimally involved (eg helping students), it is better, I can follow the teacher too and I will not die of boredom. . . (eg helping students), it's better, I can watch the teacher too and I won't die of boredom. . . (proto) tandem ftw.
I argue that at more than two or three hours, listening (unless the teacher uses methods I don't know) is not beneficial; if I am at least minimally involved (eg helping students), it is better, I can follow the teacher too and I will not die of boredom ...