Classes shouldn't be any more than an hour I feel so tense after an hour

I remember one summer college class I took was 2 hours and 45 minutes with a 10 minute break halfway in between. And that class was twice per week. That one was a pain to sit through.

There was a research study done quite a few years ago on classes. Most peoples attention begins to wander after about 50-55 minutes. Ideally a 10-15 min break and back at it. If I can find it, I'll post the link.

How long are they were you live?
In Germany they are 90 minutes.