You don’t even need to manually keep your battery in the 20-80 range nowadays since almost every charge controller automatically monitors temperature and adjusts charging parameters to not damage the battery.
Sort of. The charge controller will limit charging current if too far outside normal temperature ranges. But it will still charge all the way to 100% unless you manually limit that with the settings on your device.
Heck, lithium ion batteries nowadays last longest the longer they’re plugged in.
That’s actually incorrect, charging a Li-ion battery to 100% is significantly worse for it than charging to 80%, and keeping it at 100% plugged in is even worse. Which is why most devices will have the option to stop charging at 80% or near there instead of going all the way to 100%.
Charging while warm is also much worse than charging below 50 degrees F or so.