How important is humidified guitar storage?

It’s the most vital part of consistent play. Wooden instruments are at their best when stored in a stable humidity environment. That’s usually between 40 and 60 RH (relative humidity). Making a guitar requires stability in the moisture standard. The recommended moisture standard and stability for storage is the same as making a guitar. If the humidity in your case falls lower than 40 or higher than 60, the geometry of the wood changes. This does all kinds of bad to your pride and joy. Check out this video from Bob Taylor on what Boveda (formerly Humidipak) means to him.