My 6S has a serial number making it eligible for a battery replacement. However, I have not had an early shutdown problem. I called the local Apple shop (no Apple store close but they are certified) and they said I couldn't get the battery replaced unless I was having the problem. Fine, makes sense. Then all of a sudden today the web is crawling with stories about 6s exploding batteries, and it sounds like these are the same batteries discussed in the early shutdown problem. Will they still not replace them until it blows up or develops the early shutdown problem? Here's a link from today:
https://www.yahoo.com/tech/iphone-6s-reportedly-explodes-post-085214234.html
https://www.yahoo.com/tech/iphone-6s-reportedly-explodes-post-085214234.html