Setting 6 is the advertised 1.5 years (15,000 hours). Setting 6 is great for low light if you're not using any kind of white light illumination. Given that everyone uses a white light, setting 6 is not enough.
I don't have any newer SF lights with sun-like lumen numbers. Most of my stuff is 300-500, and I find setting 7 to be sufficient with my white lights. Outside, during the bright midday sun here in FL, setting 8 is the bare minimum with 9 being much better. It seems others are finding the same, so the advertised battery life numbers are turning out to be pretty meaningless.