If you feel like your bike light is not lasting as long as it should, the best way to confirm this is to do a runt time test.
To perform this test you will need a timer and either a small fan or a really cool area (40-50 degrees) to perform the test, keeping the light at optimum performing temperature.
1) Give the light a full charge so that the indicator light is a solid green.
2) Turn the light on High mode (first mode when you turn on the light).
3) Start timer. Check on the light every 15 minutes to see if its still running
Urban and Taz lights - 1.5hrs on High
The Imjin 800 with a 2 cell battery - 2hrs on High
Seca lights with a 3 cell battery - 1.5hrs on High
Seca lights with a 6 cell battery - 3hrs on High
*Seca 2500 with a 6 cell battery - 2.5hrs on High