MinnFlyer is correct.
In addition, when mine gets low on juice I can hear a pulsing sound
from the motor. There is still plenty of time to land.
I get from 8 to 12 minutes per flight/battery.
When I fly glow I usually land after about 10 minutes.
The flights are similar in time so not a lot of difference gained
from going to glow.
Good Luck,
KW_Counter