How long does the vanilla, orange oil, etc. mosquito repellant remain viable once mixed?

I don't use the vanilla mix-doesn't seem to work for me but I have one that is mostly eucaylptus-no deet-and organic, supposedly. Stays working at least 4 hrs.

Patty

Sorry--I didn't make myself clear--I wanted to know how long the mixture would remain viable in the bottle--not on my skin. But thank you for the information