I live in Phoenix also and I use all of the above planet wave and the several dampit models that look like a piece of hose (they work best in my opinion) but nothing beats a room humidifier especially in the winter when the heater sucks the moisture out of the air. The most important thing is the hydrometer and keeping as close to 50% as you can. I don't know if it's as critical as some say, I worry about it a lot and do everything and I play with a friend who does absolutely nothing and has not even thought about it for 10 years and our guitars look almost identical