Humidity is not really much of a factor for a solidbody, the majority of the wood is sealed by the finish, rosewood and ebony fretboards can usally stand to have a good treatment of whatever one believes is a good oil, but thats about it, humidity just makes for rust and corrosion, Accoustic guitars are a different story, only the outside of the body is sealed by the finish, the inside absorbs moisture or dries out depending on the conditions and their is the problem, unequal expansion and contraction, a fast rise or fast drop in humidity and you have the potential for a cracked top or back, but even worse than humidity is temperature drop , leave an accoustic, or solidbody in a cold car overnight and if the top doesn't crack, the finish probably will, the finish on solidbodies will usally crack or check, I put a pretty good crack in the finish of an accoustic by forgetting it on a cold night, once!........