Silicon spray is often touted as keeping Latex larp weapons in good condition, but how effective is it? Is it worth the money? What environments does it protect against?
Please note, I mean this sort of weapon, not a boffer weapon.
I've found they do help. Mostly they stop weapons sticking to each other and stop them picking up fluff.
Note that you can just buy a silicone spray from your local hardware store. The ones the larp weapon sellers sell aren't special in any way.
You can also use talcum powder to do the same thing, but it does tend to take the shine off the weapons (which I prefer for wood look weapons).
In general, silicon based products of this kind are used as lubricants and sealants. I would imagine, in your case, that it would water proof the prop and make removal of other kinds of debris easier - similar to camping equipment. It may also help prevent minor abrasions - because it's lubricated.
Is it worth the money? That's something only you can decide. How valuable is that sword?