I did not find anything in the manual that directly answers your questions. My own experiences suggest runtime is going to be very close to the stated runtimes (depending upon the battery used) but I do not measure runtimes so my guess is only a guess.

I have used turbo mode for several minutes at a time (multiple times) and have not noticed any stepdown. Thinking that was a bit odd, I’ve specifically paid attention (while in turbo mode) to see if the flashlight steps down and I’m just not noticing. The manual clearly states that the MH23 has thermal protections, so that leads me to believe the light will stepdown at some point, but I haven’t had that happen yet.

I have ran the battery down low enough that the flashlight wasn’t responding in its normal manner and turbo mode just wasn’t available, but recharging the battery took care of that.