Interesting question this one. Lithium Ion batteries are under the least stress when they are 50% charged. At 50% there are roughly equal ions on each side of the membrane. You'll probably notice that when you buy a new phone or battery device, they come from the factory with 50% charge. The best approach for battery longevity is to maintain the battery at or around 50% for as long as possible. If you're going on a road trip, try charging the battery to full as close to departure as you can (use scheduling). When you arrive with no EV range left and you're not planning a long journey, try charging it back to around 50%. You can't take the NX battery below about 30% anyway and so cannot run it down to 0%.