The last two times I had my mac running on battery...it shut down for no reason (first time at around 45% of the battery left and today at 65%)!! I was looking at some battery exchange that Apple did or is doing for some specific serial number batteries, but mine was not in the category. Is it time to change it?? I have it for about a year now (2.16, 128MB, and upgraded to 2GB). I didn't think I would have to change it so soon. Also, I have been wondering for some time..I keep hearing people saying that when you have the pc or mac plugged in, you should take out the battery. is this a good idea?