I've seen people keep humidifiers in guitars and violins. I'm not sure it's necessary as long as the humidity in your house is fairly stable and not super low. I have a humidifier on my furnace which I set at about 35% or so.
Pat, I have had good experiences at HMT. However I have not been there since I moved to Fairfax from Silver Spring in 2006 so my info is a little outdated. How long is the crack now?