Read the manual. My Stinger DS LED had a specific section that addressed some "battery myths" and how to charge this one.
Most rechargeables are good to run down about halfway, then fully charge. Depleting it completely will reduce its ability to attain a full charge after that. Maybe charge once every 1-2 weeks depending on your usage. Leaving any battery ON or OFF a charger for extended periods of time will always shorten its service life.