I've read that MBPs are designed to run forever and that a lot of people never shut there MBPs down and only let them go to sleep. What's the longest most of you have gone where you don't shut down your machine but just let it go to sleep when you're done working? One month, a year?? How safe is it to carry it around in a backpack while walking around school when in sleep mode? What are the advantages besides faster start up in only allowing to go to sleep rather than full shut down? How long will a 100% battery charge last while in sleep mode?