For most of us, charging our electronics gadgets overnight so we wake up with full batteries is the most convenient thing. For best practices for your phones, tablets and laptops though, this can be quite damaging to your device since they may constantly be overcharging.
It is however not the same for Apple Watches. To make users comfortable, the Apple Watch has been made such that you cannot overcharge it. You can put it on for 10 hours. After the first two hours of it getting full, the phone will automatically stop charging.
Should I charge my Apple Watch 3 every night?
Charging will stop automatically when the battery is fully charged and start again if and when required due to ongoing background battery usage. Quite unlike the iPhones, you can charge your Apple Watch for as many as you wanted without risking its overcharging.
Notable is that it is impossible to turn the watch off whilst it is on the charger and connected to power. It is also normal for your watch, power adapter and charging cable to become warm when connected to power. This doesn’t most mean your phone is overheating.