In 'note taking mode' (no wireless, minimum screen brightness, max battery saving mode) you'll get 4.5hrs (or more) from all of those this year. Next year? Probably 3.5 hrs.
I think you'll see a lot of freshman toting laptops around. Not quite so many upperclassmen. They leave theirs chained up in the dorm most of the time.How to not look like a freshman