UltraFire WF-606B

I just received an UltraFire WF-606B. It's a cute little light. Glass lens, lightly textured reflector, Cree emitter. Type 2 black anodize. It'll take either a CR2 cell, or a pair of AA cells. I bought it because I wanted a CR2 powered light.

I don't really have any complaints about it, except it seems like if the anodize on the threads wears through (and it will, because it's type 2) I won't ever be able to turn the thing off. It's a twisty, not a clickie. There is a spring in the tail of the light, so the battery doesn't rattle (which is nice), but the battery is always in contact on both ends. The negative contact ring in the head isn't isolated from the rest of the pill, so the entire head assembly is essentially the negative contact.

Has anyone seen any problems with these little lights not turning off?

Take a very close look at the "pill". I'll bet you'll find that the emitter board and converter board nest inside a nylon tube that threads into the head/bezel. This nylon insulates the negative outer ring on the bottom of the converter board from the metal head/bezel.
The battery tube contacts the negative outer ring only when you twist it all the way in.
Metal on metal contact at the threads will not effect the electrical operation of the flashlight in it's stock configuration.

Good guess, but no. I think that's the way my Fenix L0P is built, but this UltraFire is not like that. There is no isolation between the pill and the head. I'll try to get a picture of it tonight. The pill threads out fairly easily. It's all metal, with no plastic or nylon to isolate anything. The negative contact ring on the backside of the circuit board is soldered to the body of pill.

There are already some worn spots near the very end of the body tube thread. The light will flicker on a bit just as you start to thread the two pieces together. It seems to stay off after you get past the first turn or two. I'm just worried about long term reliability, or having this thing turn on while it's in my pocket.