How long your bike lights last has to do with the power source you use to power them. For example, you have headlights and rear lights that are AA or AAA battery-powered. In addition, you also have bicycle lights and rear lights with an internal battery, which is rechargable. On average, battery-operated bike lights last between 50 and 100 hours. Lights with an internal battery don't last as long on average, but don't need new brand batteries every time. So think about how long you will need your lights and how often you would like to recharge them. Important tip: always switch off your lights when you are no longer cycling. This is often forgotten!