[asendra]

Just my case, but Apple replaced my 6s battery because of random shutdowns under the replacement program on Jan 17th.

Around the release of iOs 11 (not sure exactly when because it was gradual and I was also on the iOs 11 beta) my 6s became incredibly slow, almost unbearable, until last month I decided to upgrade to an X because of how slow it was. Was planning a year more but I just couldn't see myself using it 1 year more.

Now I see via CPU Dasher and Geekbench that my 6s with a battery less than a year old (95,7% original capacity, 406 cycles) is running at 1400-900Mhz, (almost always between 1200-1000Mhz) instead of 1800Mhz.