Leave the battery at 50% state of charge (SOC) in a cool room, and it'll last more or less forever without degradation. That's why everything you buy that contains a lithium battery arrives half-charged. Move away from 50% in either direction, and over time, the battery will age and will be able to store less charge. If you keep the battery in the range of 20-80% SOC, it'll age but at a reasonable rate - say 10% capacity loss over 10 years of normal use. 20-80% is a reasonable compromise with usability/readiness if you want to own the car for a long time. People who lease their EVs for a few years often don't care about this (or the next owner?) and charge to 100% every day because a fully charged car provides the most utility for them. Frequent DC fast charging degrades the battery somewhat quicker, around twice as fast as no DC fast charging. Occasional DC fast charging for road trips is fine and is part of the intended use case of the car. The other thing to try to avoid is leaving the car at 100% SOC for very long, particularly in hot weather.