Regularly syncing your Nike device to your computer's USB port ensures that your workout data does not fill your device's memory.
The devices that require syncing data to NikePlus via Nike+ Connect include the Nike+ FuelBand SE, first generation FuelBand, Nike+ SportWatch GPS, Nike+ SportBand, and Nike + iPod Running Sensors.
Although your device can store 1-3 months of activity data, Nike recommends syncing three times per day for best results. If your device's memory is full, you will not be able to record workout data until you sync your device to your computer.
Performing a factory reset will also clear memory on your device.