> Stock iOS has two separate low-battery alerts, the first of which occurs when there's still a fifth of my battery left!
Recharging after the first 20% alert might significantly prolong the useful lifetime of your battery. Li-Po cell can provide a couple thousand 80%-20% cycles, but only less than a thousand 100%-0% cycles because working at the ends of the capacity range degrades the battery faster.
It's a fair point. But for me on my iPhone 6S, I've found that last 20% to be the difference between a phone that gets me through the day, and one that does not.
I get my battery replaced yearly. I would upgrade to a newer phone instead, but I value my headphone jack too much.
Recharging after the first 20% alert might significantly prolong the useful lifetime of your battery. Li-Po cell can provide a couple thousand 80%-20% cycles, but only less than a thousand 100%-0% cycles because working at the ends of the capacity range degrades the battery faster.