When Apple admitted to this, they initially thought offering their $79 battery for $29 would make this problem go away. Well, after 24 Class action suits were filed in the US and who knows how many internationally, Apple's in more trouble than they bargained for. I personally could not even make an appointment at my local Apple store because they were so backlogged, they were not even setting future appointments at that time. On the positive side, there's a rumor that Apple is running out of the replacement battery for the 6+ model and is upgrading those for free to the 6s+.
The main reason to replace batteries on these models is not just for extra time before it goes dead, it's because replacing the battery also un-did the speed throttling of your processor. Apple just announced that it will not be necessary to install a new battery to get your original faster processor speeds back. They are releasing new iOS 11.3 that brings new features. Buried in the list of features is the fact that it offers battery management features. One is the ability to turn off the "Power Management" feature.