Been on 14 since release. Haven't noticed a drop in battery life. Then again, I didn't have that issue with any of the previous phones with the exception of my 6S which had the faulty battery that was replaced under recall.
Generally the phone can go all night playing music, and goes probably two days without a charge if I want to stretch.
But honestly, I never do stretch it out. I charge it in the car on the way to/from work. So its on the USB charger for about 40 minutes a day. The car's USB port is SLOW at charging the phone. I usually supplement by plugging in at work if I need it.
Battery health is at 85%, phone is 3 years old. Plan to keep it until its unusable. I like the cheaper phone plan cause there is no device payment on it.