When the green button turns red, that's your cue to switch to low beam.

My evening commute averages around 40 minutes this time of year (I have daylight in the morning). Today I tried to get a third run out of it before charging, and wound up doing the last half of the ride on low beam after getting the low-voltage warning. So I guess my four-month-old battery is good for a little less than two hours of runtime on high (temperatures have been a few degrees below freezing here).

ItsJustMe, how is your 8-cell battery working out?