for years I would give the fretboards on my guitars a quick spray with furniture polish whenever I changed the strings, job done, no disasters.
I'd just bought a high quality classical guitar and the fretboard looked a bit dry,bought a bottle of this and gave it a go, looked a lot healthier straight away, definitely a big improvement on furniture polish,smells nice too, you only meed a few drops, so a bottle this size will last you forever