BT Waves Bluetooth Headset uses lithium-ion polymer battery.
Here is an extraction on how to prolong the life of a lithium-ion battery, with great technical explanation.
1. Avoid full discharges and charge the battery more often between uses, but do not keep it in fully charged status for an extended time.
Partial discharge on Li-ion is fine. A partial discharge reduces stress and prolongs battery life. There is no memory and the battery does not need periodic full discharge cycles to prolong life. Similar to a mechanical device that wears out faster with heavy use, the depth of discharge (DoD) determines the cycle count of the battery. The smaller the discharge (low DoD), the longer the battery will last.
Be aware though keeping the battery in fully charged status for an extended time can be more harmful than cycling.
2. Avoid exposing the battery to high temperature.
Lithium-ion suffers from stress when exposed to heat. Elevated temperature (above 30°C or 86°F) hastens permanent capacity loss.
3. For optimal performance, charge the battery at a voltage of 3.92V/cell.
High charge voltage also stresses lithium-ion batterys. For most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. On the negative side, a lower peak charge voltage reduces the capacity the battery stores. In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms.
(Technical source: http://batteryuniversity.com/…/how_to_prolong_lithium_based…)