Do threads and tailcap buttons need lube for waterproofing?

Should the rubber boot/button have some lube/gel around the edges inside the tube for increase waterproofing? This question is for the FourSevens MKIII, but I notice my Fenix LD20 is similarly constructed. The question is, is the bone dry edges between the boot an seal more likely to leak than a light with a little bit of waterproof lubrication on the edges of said boot?

it's unlikely to leak when dry, I'm assuming we're referring to the tail clicky. the usually construction for these is boot - washer - switch - locking ring. when the locking ring is tightened it pushes the switch I to the washer which clamps the rubber between it and the tail cap. being dry will cause no issue and it's a non moving part. if it were greased it would likely try and squeeze out from.beyween the washer and tail cap under pressure. also due.to the clamping force it is highly unlikely that it will leak.

If I have a tailcap apart I usually smear a little silicone or superlube on the edges of the boot. It's never caused a problem and if it helps, great. I figure a little waterproof grease like this can only help.

I also like to very lightly rub some silicone grease on my no -captive switch covers like maglite uses.

keep the o-rings lubed, and you will be ok. The threads will not be waterproof, but it's fine to lube them to make it smooth. But in the end, it's the o-ring that will keep the water out.