Hi, I have a 2008 macbook, it's been having some problems so i'm getting the hard drive replaced, but it got me thinking about its longevity. It has served me well and I see no need to replace it, as long as it can last, so how long can I expect it to last? It would be great if it could last another 4 years. The battery is gone, and I don't mind keeping it plugged in, using external keyboard, screens, etc. But what on the computer(beside the harddrive, screen, keyboard, mouse) is considered a wear item that may not last for another 4 years? I know, if need be, I can upgrade the ram, but what else might cause problems? thanks!