The smart batteries will automatically discharge them to 50% if you leave them long enough, by default this is set it 10 days. You can change it via the DJI go app. So after each flight if oyu know you are not going to be flying for a while its best to charge them to at least 50% as its worse to store a battery for along time undercharged. If you want ot learn more about general Lipo battery care check out our lipo battery guide.