Thanks for the info... its good to know, but the good news is it isn't quite as bad as you thought.
It doesn't drop from 600 to 60 after 1 minute.
Per the manual for the Valkyrie Mini, "The LED light will work for one minute at the top output mode and gradually step down to 60 lm within 10 minutes."
I decided to try mine out to see how reliable it would be.
Fully charged, it was extremely bright with no significant drop for ~4 minutes. It did begin to get a but dimmer after that, but not enough to limit effectiveness. It was still blinding if it were pointed at a person for about 10 minutes. At 12-13 minutes it was no longer blinding, but still lit up a room at the far end of the hallway (~40 feet). At ~15.5 minutes, it was enough to keep from tripping on something... it was like holding a candle. It did not dim noticably after that... so I'm guessing that was the minimim 60 lumens or close to it.
So my verdict... not usable as a duty light, but still very good for home use. Fully charged you can trust it for 12-13 minutes, much more if you use it intermittently. Not useful after 14 minutes, except to keep from walking into walls. I have very bright flashlights all around my house and in all my cars, so this is not an issue for me. Comparing to other lights I'm pretty sure mine was at least 200 lumen or more after 10 minutes, not 60, but its new and fully charged. 60 after 10 might be an average.
I plan to check out the Baldr mini tomorrow and see how it behaves.