+1. You don't finish Ebony. Oil it every once in a blue moon if you feel like it. Some guys use lemon oil, others like linseed oil, still others use mineral oil. I've always left mine dry for years on end, and haven't suffered for it.
Note that the "Fret-Ease" and "Fast Fret" products some like to use to "speed up" their playing is nothing more than a dramatically over-priced tablespoon of mineral oil in a specially-marked applicator. If you use that, you never have to oil your 'board. But, it'll make it greasy and difficult to play while gunking up your strings. So, whatever's best for you.