Samsung SPH-A680 / VM-A680

Hi. I've had the Samsung VM-A680 phone for a month now and it's a great phone. I recently bought a desktop charger that allows me to charge the phone while also charging a spare battery simultaneously. I want to keep the phone in the desktop charger while I'm at home just to keep it fully charged throughout the day so it doesn't run down as I'm using it 😉 . But my concern is that this might negatively affect the battery life over time. Can anyone help?