There just appeared a scientific paper Woody et al. (2020) on optimally preserving the capacity of Li-ion batteries as used currently in electric vehicles. While the battery for my own electric vehicle is rented, this is still highly interesting advice, which also comes in handy to manage batteries for my model aircrafts.
Unfortunately, that paper is behind a paywall (don’t get me started on Elsevier), but Elektrek has a nice summary (thanks!).
Main simple rule: avoid to run the battery all the way down.