Every device that uses lithium cells has their own charging procedure - Some charge to only 4 volts, some to 4.1 and some to 4.2 . . . . or some number in between. It's true that using a lower voltage makes the battery last longer because it's not charged to 100% of what it could be, and pushing closer to 100% is harder on the battery, but gives you a larger watt hour capacity . . . . for as long as the battery lasts
So, keeping it to 80% of the 'maximum charge' is better for the battery, especially in hot weather than a 'full recharge' . . . . if that's important to you
Others may disagree with my use of 100% charge for when charging on our cars stops, but that's 100% of what you can put in as the protocol won't let you go any higher. So 'full charge' and '100% charge' are the same thing to me - The most energy you can put into the battery pack - Granted, that's less than the battery could hold if you pushed things, but we can't do that. A full charge is all we can do and no more
Don