It needs to be recharged after up to 18 hours of use.
The AppleWatch7 can stand up to 18 hours on a single charge. But heavy use only lasts about five hours.
If the battery life is maintained for 18 hours, it can support 90 checks (5 per hour), 90 notifications (5 per hour), 45 minutes of app use, and 30 minutes of music via Bluetooth.