Earlier quoted context omitted.
That quote really hurts. My iPhone 6S has had spontaneous shutdowns since the first winter it was out (and is supposedly not in the replacement program). No previous Apple phones did. This winter it's the same. To me it suggests a more widespread defect that they do not wish to admit.
FYI - https://www.apple.com/support/iphone6s-unexpectedshutdown/ that was effected by a recall. You should check your serial number.
Just got a brand new battery today after 2 years of usage thanks to your comment.
Thank you. You just saved me 80$ from paying to replace it myself.
Now I can justify to myself that it pays to read hacker news ;)