It seems to me that the battery life on my 3GS has declined significantly in the past week or so. I used to quite easily go the whole day without getting to the 20% warning, but now that happens by about 4:00 or 5:00 PM. The phone isn't all that old (maybe 1.5 years?) - is that long enough for the battery to go? Do I now have to send it in to Apple or take it to an Apple store to be replaced? If I go to the Apple store, can they do it right there, or does it take a while?