If you have some dielectric grease (typically bought at auto-parts stores to put on spark-plug wire boots), that's a good O-ring lube. Try not to get it on the bare metal parts of the flashlight that are intended to transmit electricity, though.
Holy crap is that sucker bright! My wife thinks it's too bright to have on the highway. She called it a spotlight. Whaddya think? Is it possible for it to be too bright?
You could get a Dereelight DBS V2 with the 1S R2 pill and the smooth reflector, and show her what a bright light would
really look like
Aim it at some trees 1000 feet away. "See, now I'm leaving the DBS home, dear, and just taking that other one... OK?"
In all seriousness, though, if you think it might be too bright, go do a quick 2-person reality check. Drive your car while someone rides your bike towards you in full darkness with the light aimed the way you like it, and see what you think.