What they should do is to allow user to switch between standard (works like now) mode and battery-conservation mode, where user does not care about battery and system does its best to preserve battery health. I'm using my laptop on charger 99% of time and when I need to transport it, I could switch that mode few hours in advance.

The happy range for a modern battery is 20-80%.

The bottom and top 20% are what's causing the wear, so merely staying between 90% and 100% won't do you any good.

Source? If you are letting charge drop in that range and charge again, you are creating charging cycles. Charge cycles reduce the capacity of Li-Ion batteries.

https://support.apple.com/en-us/HT201585