How often should fretboards be oiled ? I never oil mine, I just wipe them down with a damp cloth
There is no set frequency. As with most things, it depends. My suggestion would be to condition the fretboard/fingerboard of each instrument at least once per year, depending on what kind of wood it is, the climate in which you live, how often the instrument is out of the case and exposed to the elements, how often it's played, and thus forth. The more porous kinds of wood, like rosewood, pau ferro and cocobolo, for example, will need it more often than the less porous varieties, such as ebony and maple. I'm not sure whether maple
ever needs conditioning.
All my instruments - guitars as well as bass guitars - have ebony boards. I condition them twice a year: in the fall, to protect from the cold, arid air of winter; and in the spring, to help the wood recover from any stress it might have incurred during the winter.
By the way, I used the word "condition" rather than "oil", because I've found Gibson's Fretboard Conditioner also does a fine job (though it probably contains oils). I've switched off between using the Gibson product and instrument-grade lemon oil, both with excellent results.
MM