Ylo2 said:
Spend a few bucks on a humidity meter (Radio Shack has them), then keep the humidity as close to 40 to 50 percent as you can all year around. Outside of this range, wood shrinks or expands. You shouldn't have a problem with most electronics unless the humidity gets close to 100 percent or condensation forms on electronic components from a sudden drop in temperature.
+1
I picked up a digital, accurate hygrometer along with the calibration kit:
http://www.amazon.com/HygroSet-Adjustable-Round-Digital-Hygrometer/dp/B000H6CZQE/ref=sr_1_1?ie=UTF8&qid=1300669840&sr=8-1
and
http://www.amazon.com/Boveda-One-Step-Calibration/dp/B000A3UBLA/ref=pd_bxgy_k_text_b
and make sure the humidity is always between 40-50%...sometimes it dips down to 37% or so, but that's when I usually kick on the steam-humidifier. It's about a 12x12, wood-floor room with a crawl space underneath. Prior to me keeping all my guitars and amps in there, during the winter, it would get as low as 22% in there. It is amazing peace-of-mind to know it's optimal in there all the time now.
For what it's worth, a few years back, when I lived in New York (and the dry winters)...I had a Washburn Nuno Bettencourt guitar...paduak wood and ebony fretboard. Well, one morning I woke up and there was a split running down the fretboard, probably from the 2nd fret, all the way to about the 20th. The freaking thing just split!! I called up Washburn and guess what? I was SOL. The best they would do is "fill" it with ebony dust and some kind of epoxy or whatever. You could absolutely tell there was a line running down the entire fretboard. I basically gave the thing away and traded it for a couple pedals, I couldn't even stand to look at it. Lesson learned.
Spend the few bucks and take care of your babies. Also....never had any issue with any of my amps/electronics, etc.