I have a question about oiling the fretboard and humidification. Here's where I'm coming from:
Over the years I've had a few mandolins, a couple Webers, a couple KM1000s, and some less expensive Kentucky and Eastman models. The Webers and the KM1000s all had ebony fretboards. The entry level Kentucky models, which I still have, are rosewood, and I don't remember what the Eastman had, I think ebony. I also have a few guitars in the house that have rosewood fretboards.
I've been pretty diligent about keeping case humidifiers in all my more expensive instrument's cases, and I keep them cased unless I'm playing them. The fretboards on both the KM1000s I owned dried out in less than a year and developed that "scalloped" look, with the fret ends sticking out; the classic under humidified fretboard thing. I never had any humidity-like issues with any of the Webers. The less expensive Kentuckys have never been humidified and have never (yet) developed drying issues. I assume this is because of their heavier build and the rosewood boards being less prone to drying. The guitars I have likewise have never shown any signs of being under-humidified.
I've been told that I haven't had drying issues with the Webers because they're built near where I live and so they're acclimated to local conditions. I've also been told the KM1000 fretboards must have been "green" or something. I have no idea if that's likely or not.
I now have a couple of new (to me) mandolins, both of which were not built in my dry climate, and both of which have ebony fretboards. I'm a little paranoid about them drying out. So, my question (finally) is what else can I do to prevent the fretboards from becoming overly dry? I'm using Oasis case humidifiers. I add water every week or so and I change out the little crystals every year. Would treating the boards with something once or twice a year provide added protection against drying, or is that more of an aesthetic thing?