Hey, for some reason my MBA is only lasting for 2-3 hours before it dies. Also, the fan seems to be running more often. It's my first Mac, bought it in July 2012. I used Windows for years, even built my own tower once. But I'm still a Mac novice. So I don't know about any basic diagnostic tools or steps, even system restores, that I would normally do with a windows machine. Any advice?