Noob alert. This is the BLF and not the other site so :
I just received my iTP A3 from goinggear and really liked how smoothly the head screwed off. The o-ring on my Powerlight had broken off and the threads were squeaky and gritty. I suddenly thought of teflon tape ( http://en.wikipedia.org/wiki/Thread_seal_tape ). I've never seen it mentioned here or there. Anyway, I used one single layer of teflon tape on the Powerlight threads and screwed the cap on. It actually seems to have worked quite well. I realise it is non-conducting etc. But I suppose it can be used in emergencies or when you don't want to use or don't have either lube or a o-ring. Serves two purposes - seal & lube. Non-messy too. Very very cheap.
I'd say bad idea. Teflon tape will deform with constant usage very, very quickly. If you want cheap, reliable lubricant get lithium dielectric grease. Cheap as all get out, non-conductive, and it won't break down rubber.
I wouldn't use it unless the threads were real sloppy. I use it on a Q-Mini to help prevent mode jumping due to the sloppy threads, but it does wear out fairly quickly.
With sloppy threads it works well, though you do have to keep an eye on how current is going to get through. This light has had Teflon tape in it to tighten and smooth the threads almost from new. The tailcap has nothing to do with current conduction - it is a twisty with a spring-loaded plunger which can be fastened down with the tailcap. This is the second most expensive light I've bought, but the threads aren't great. Teflon tape has worked wonders.
Elektrolumens triple Luxeon K2. It was fearsomely bright when I bought it, less impressive now. I have a 14500 light that approached double the output (Briefly) It gives around 250 of my lumens.
It has a large chunk of copper inside it for heatsinking. It needs at the very lest an emitter swap to more recent TFFC K2s.
It is direct drive (There is a little resistance to tame the heat) using 4C NiMH.
If you run short of lubricant then squalene is always with us, rub your finger down the side of your nose or stick it in your ear, squalene , an excellent lubricant