Well, here's the quick version: I got a pair of the lights and noticed that the more I used them, the dimmer they got. It was not a battery problem--I had a "good" light and a "bad" light but eventually they both turned bad. Output power dropped to about half compared to when they were right out of the box.
The vendor replaced them, and the replacements did the same thing.
If I look closely at the emitter I can see it turning brown. One of the lights now has an uneven light pattern as some of the 4 emitters are working better than others. It's easy to see that some of them are discolored.
So I am 0 for 4 on these lights and I am not sure what to do about it. I think the vendor will treat me ok but I don't even know what to ask for. If I keep paying to send bad lights back, these lights won't be a deal for much longer.
There must be a bad batch out there. But hey, they didn't flood!
Later I'll post another thread with some pictures and measurements. Right now I am still recovering from my Roatan vacation.