I fly drones/quadcopters that use LiPo batteries and they have built in discharge functions but the default is 10 days. I set my batteries to 3 days. I may charge them the night before to 100% even if I'm not going to fly until 18 hours later though. And then, if I don't go fly it will be 72 hours before they start a slow discharge on their own. It would probably be bad over time to charge to 100% and keep the car plugged in and charging set to 100% for many days in a row without driving the car.