I've never turned off my PowerBook. Simply close it, make sure it goes to sleep, put it in the case, and go. It will resume from sleep in less than a second, so it's very useful to do something quick and store it again. If you have Wifi on your campus, it usually connects to a known AP within 2-3 seconds from waking.

The sleep and Wifi functionality alone was a big driver for me to switch from Windows, where it is less reliable and much slower.