My 5th gen is having issues. One moment it will show that the battery is around 80% and then the next minute I get the 20% warning and it dies not too long after that. I usually have it plugged into my car stereo so this doesn't matter, but at some point I would like to use it by itself and obviously it's not going to work with this issue. My question is - is it worth it to have the battery replaced, or should I just buy a 6th gen? Mine is 64gb and I have 6.5gb free. If I would upgrade I would get a 128gb for future proofing.