It’s actually true - Any battery has a nominal percentage at where to both discharge and charge to, to extend battery life by a great deal.

E.g for your phone, it’s roughly at 30% to discharge to and 70-75 to charge to.

You don’t have to do this though!

And think about it … if Elon can sell you a new battery faster than expected … It’s not like there’s any reason for him to tell you about this 😂