BMW does a few things (probably more) to help maintain the batteries' lifespan.
- active heating/cooling to keep them within a safe range
- limit the min/max of use usable versus factual SOC
- tapers the charge both at the beginning if hot or cold, and at the end to help prevent thermal problems and overshooting
- limits the maximum duration of maximum power allowed (most people probably never experience that)
They believe enough in them to put an 8-year warranty in the USA. Now, yes, on something like an i3 with the CFRP frame, plastic panels, and electric motor, you could likely keep it beyond that time, but the state of the art may very well prompt people to get rid of it before the batteries actually become a major factor of ownership.
The only way to probably limit the max charge level on an i3 would be to have a programmable EVSE that you could estimate when the charge level would get where you want, and tell it to turn off, or have a home automation system to cut power to it. MOst EVSEs will recover from a power interruption, but not all, so double check yours first. Some require you to remove the plug and reinsert it to restart its sequence.
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)