Hi cnmrc, Jacob here, I can see you are worried about your battery health of your iPhone. Battery health is a measure of battery capacity relative to when your iPhone was new. Lower capacity (%) may result in fewer hours of usage between charges. It is generally said that anything above 80% is acceptable battery health, and that with the lifespan of your iPhone being 2-3 years 20% over those 3 years is considered acceptable, However, I disagree, I usually fid that by 84% the time between charges becomes too low, that is however based off of my usage and lifestyle. Lithium ion batteries (The battery in your iPhone will naturally degrade) However, 95% battery health is perfectly fine and can support normal operation of your device. However if you are concerned, you can have Apple replace your battery for a fee, You can find more information in the support link, which I will put t the bottom of this thread. You mentioned prevention of degradation. With lithium ion batteries, Keeping your iPhone outside of direct sunlight and inside its standard operating temperatures can all help to preserve that percentage.
iPhone Battery Repair & Replacement – Apple Support (UK)