Hello,
Due to the amount of use iPhones get, their batteries are in a constant state of discharge/charge. Personally, I try to keep my iPhone 6s/iPad Air 2 batteries at 50% or more, and don't really worry about the battery duty cycle/lifespan of those devices. Because they are used on the go much more than any of my portable Macs, it is more important to me to not run out of charge. I dislike having to drag around a charger with me for iOS devices. When on the road with a MBA/MBP, I carry it in a bag, so bringing the AC adapter along isn't a worry. One nice thing about iOS 12, is that it will give you a good indication of battery health in Settings > Battery > Battery Health. Macs don't have as much information about their battery.
C
I suppose I've simply elevated "anality" (did I just invent a new word?) to a new level fretting over my iPhone battery. I carried a 128GB iPhone 6 for a long time, and even after replacing its battery during the Apple BatteryGate thing and the $29 replacement, I fretted too much about it. I've long been in the habit of carrying a Lightning cable and charger with me, even though I only ever needed it once, when my father was hospitalized and the family was keeping vigil there with him. My little sister's iPhone was constantly running down, so that's what ingrained that habit with me.
Since then, I've acquired a few of those little portable batteries, mostly to give away as gifts (especially to my sister and Mom, to whom I have my iPhone 6 when I bought my XR). Those little puppies are dynamite, and surprisingly affordable. A few months ago, I bought a nice set of Rowkin earbuds, and its carrying case has the ability to charge phones. I only used it on my XR once as an experiment when I deliberately allowed my battery to deplete to about 25%, and the Rowkin's battery brought me back up to 60% really fast. (What I don't understand is why the Rowkin battery will charge my son's and daughter-in-law's Samsung S10s so much faster than it will my iPhone.)
I really shouldn't obsess so much over my phone's battery I suppose. But even with my discount as a shareholder, I'm still known far and wide as being really tight-fisted with my money, so much so I've been told I can make nickels squeal and turn purple. I've never minded forking over a lot of dough for my desktops or laptops, but I hate spending money on something so vulnerable to damage, loss or even theft as a phone. On top of that, the XR does retain its charge much, much longer than my iPhone 6 ever did.