I always print my PowerPoints 2 per page, back and front, but it is mainly due to eyesight needs. Plus, I like more room to take notes next to each slide.
Last semester, all of my classes filled a 3" binder, each. I used to go in first day with 2" binders for each class, but halfway through the semester, I always had to start a new binder ... so now, I just start out each semester with the largest binder that fits in my bag! It DOES end up taking up a lot of desktop space, though.
... And, now after reading some of these posts, I am thinking of just bringing smaller binders to the actual classes (for the sake of desk top space) and then transferring the materials into the larger binders when I get home.
The main problem I can see happening with this method, though, is that many times, I have found myself referring back to previous materials while I'm IN class ... and with this new transfer method, those would be at home.