Bass Case Humidifier to combat Ebony shrinkage?

Another dry and cold winter is threatening my beloved ebony boards (MI winter humidity v CA conditions = shrinkage of the George Costanza nature). My Alembics have moved from the wall to their cases. Has anyone used any bass case humidifiers and were they worth it? I'm trying to be proactive and avoid any protrusion of fret edges, which is a commonly noted problem with humidity shifts.

Thanks.