Indeed, from a shelf life point of view stop nearer 4.0v than 4.2.

Many modern controllers can be programmed to do this.

Most battery chemistries have some limitations like that - e.g some lead acid types are best not discharged below 50% - which does mean taking the headline Ah rating with a large pinch of salt.

   - Andy.

I don't know where the 50% figure comes from.  The range most people quote is 20 to 80%, which is a lot more useable.

But in reality, it's not that simple.  If a battery management system is designed to maximise the life of the battery, then it will reserve some capacity at the bottom end that it never lets you use.  So if the battery gauge on the car says you have hit 0%, the battery may really have 10% left in it.

The management systems are also careful not to over charge.  Which is why they switch to trickle charge for the last bit.  Watching a recent Julian Ilett video, it looks like his MG allows you to choose between a battery saver mode that stops charging at 80%, or long range mode that gives you 100%.  That sounds like a very sensible idea.