I'm responsible for several iPhones used by family members. One a 2-year old iPhone 7 with the battery health down to 84%; that's a no brainer to change by Dec 31 with the $29 pricing. The other is a one year-old 8 Plus with battery health at 94%. Because that phone likely will be kept for 3 years, I plan to wait another 6 months and then replace it, even if it is more expensive. The last is my iPhone X, which is down to 94% (and has been that way for several months); I plan to keep it at least another year. I know Apple's spec is that a battery is not bad/degraded until it hits 80%, but do folks recommend replacing a battery even if it's only a year old and still above 90% capacity?