You've found bad advice. Stop doing that since Lithium batteries do not need this. You are needlessly wearing out your battery.
I've had the iPhone 7 (Bought unlocked from Apple ) since beginning June 2018.
It's been used and charged well. I've mostly charged it diligently between 50 to 80%, and let it run down to 25 every few months, and then charged it up to 100%.
Less than a month ago I updated to iOS 12.1 and I can see that there are fewer bugs and the phone is running pretty smooth.
However, today I went into the battery section and noticed that the Battery Health is now at 99%.
Peak Performance Capability is normal.
It's just been 8 months and there's already a 1% drop in health. Should I expect to have to change the battery before this year is out?