Most of the flashlights we sell run off of lithium based rechargeable batteries. If you have a spare moment we suggest you read the below article about prolonging Lithium-based batteries life span.
How to Prolong Lithium-based Batteries Life Span
Some of the key points taken from the article are listed below
1) The shorter the discharge, the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life.
2) Do not store lithium based batteries with a full charge
3) Remove the battery as soon as it has completed charging.