We keep our shop at 60-70% humidity depending on the season and recommend these numbers for all our models, especially our 80 and 900 Series guitars which have a higher-level bracing system. All guitars from all manufacturers must be stored in minimally 50% humidity at all times. On higher-level acoustics like our 80 and 900 series we recommend over 60%.  If not the woods will warp causing playability and sound issues and will eventually crack. Damage can happen in a matter of weeks if conditions are severe.  New guitars with high-quality solid woods and low action are most susceptible.  Less expensive guitars with high action will not be affected like a precision-made solid wood guitar with low action.  This type of damage is not warranted by any guitar manufacturer but it is repairable.