I did a few forum searches on the battery lifetime. What I could find was that they'll last anywere between 2 to 6 hours. Don't know if that was with or without sound. But most people said around 3 hours of continuous use.
I'm waiting for my first sabers to arrive and probably will do a battery-life-test, so I'll let you know ones I'm sure. And if I can remember and find this threat again
My Aeon LE V3 stunt saber (Consular Green, because it matters on how much power is required) lasts overnight and still has juice to spare in the NiMH AAA 4-pack. I can grab some fresh cells and start a new test tonight.