I was searching for months at Apple Stores for a refurbished powerbrick for my 17" Powerbook, hoping such an animal even existed. One day I stumbled upon a firesale and lo and behold... a refreshed powerbook powerbrick for $29.99! Marked down from $79.99! Aside from that, many suggest to get a spare battery. Now that I have a 2nd powerbrick in my backpack, would a spare battery be necessary? Also, if I do get a spare battery, would it eventually lose its longevity just sitting in my backpack if I barely use it? Opinions would be great.