I purchased a new unlocked 6 plus and had this issue fairly shortly after a year, and ended up having to live with the problem for almost another year, because the only option provided was a full cost-replacement. When they finally introduced the replacement program, I begrudgingly paid $150 to replace my phone. They took my phone and gave me a pink 16GB loaner, as they said they had to check my phone for "modifications". After 3 or so days I received a call and went back to the store to get my replacement. Within 24 hours of picking it up, it began displaying signs of "touch disease". So I ended up having to go to an Apple store 3 times to get it fixed.
Less than six months later it started having issues again right before a big trip and since the "repairs" only have a 60 day warranty, I had to pay for the replacement program AGAIN. So I've dumped roughly $1500 and significant time into the phone. I haven't purchased an Apple product since, and I have signed up to be part of the class-action and I will do everything in my power to ensure my story gets heard. It's absolutely disgraceful a company making this much money not only doesn't support their products, but then charges their customers to fix the issue.
The best part was when the "genius" who helped me claimed the only way it could happen is if I mistreated/dropped my phone and then charged me to replace it with a unit that already had the problem direct from Apple.