Right. I didn't mean it that way. It's just that there are some lights out there that claim XXX lumens, but after only 1 minute of use they will have dropped to 75% of light output and steadily decrease. Then there are the lights that are XXX lumens which drop to 95-90% in a couple minutes, but stay in that range for a good amount of time.No idea. I'm sure someone on CandlePowerForums has done some exhaustive testing, but you'd have to search for it.
In my emergency lights, I typically don't push them to the end of battery life, or even anywhere near it. If I think I've got half an hour or so accumulated in a set of batteries, I'll change them and use the used batteries in a one cell light for utility purposes.