College students, how do you deal with taking 3-hour long lecture courses?

I'm a college Freshman, and luckily, all of my courses last 90 minutes at the most. However, I do know that in more advanced courses, a lecture might last 3 hours. Golly! I'm already dreading the idea. I've been so used to classes that last 90 minutes or less ever since high school. How do you stay focused and concentrate in a 3-hour or, whew, even longer course? Don't you get bored and just wanna get out of class at that point?
College students, how do you deal with taking 3-hour long lecture courses?
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