Room Humidifier

steam humidifiers aka vaporizers, are for medical treatment not guitars
cool mist models (evaporators) are the recommended type,
ultrasonic is the type that leave white s deposits, avoid them.

to clear up some of the confusion being spread here:
What is the difference between a steam humidifier and an evaporative humidifier?

Steam humidifiers utilize an internal reservoir to heat water and convert it into steam. ... Evaporative humidifiers utilize an internal humidifier pad drenched in water. Warm air is blown over the humidifier pad to evaporate the water which is then expelled into the surrounding area, thus also increasing indoor humidity

The pad is often referred to as a filter because it does. That is why they get hard due to calcium and other minerals being filter  out. (ie remaining in filter)

markman ,

Take far more notice of TonyKgull ,and RobertW , as they are far more familiar with your climate.
Here in the UK you just have to be aware of the humidity if on the very rare occasion a bit of humidity is required I just put a couple a fancy looking container filled with water and placed close but not to close to the fire, suppose it works a bit like a fish tank on a smaller scale.

If you don't want the calcium (white stuff) deposits the things in your room, you might try cleaning out your reservoir with some vinegar, rinse 2-3 times with fresh water and refill with DISTILLED water. It truly makes a difference. But, you must rinse the deposits out of the reservoir for it to work or they will just contaminate your distilled water.

I've been using a FREE large (2.5 gallon) console size evaporative type (with a wick and fan) humidifier for about 9 years. I replace the wick every Fall before I start using it, and add some of the bactericide every other day. I add 2.5 to 3.5 gallons of tap water to it DAILY, and most days it runs out before I get home after work. And I typically add another gallon before going to bed. At the end of the season (4-5 months) the wick is nearly solid with minerals.

It's covering the whole downstairs (about 300 square foot finished basement), which is open to the upstairs thru a hallway & stairs. The furnace pulls air from there. And the worst part, all the cold air that comes in thru the front door ends up down there. It keeps the humidity in the 40%'s most of the time, but when it gets real cold and dry I struggle to keep it mid 30%'s.

I've thought about building a larger ultrasonic unit with an automatic fill and humidistat, but if either of those fail I could end up with a flood or 100% humidity and water dripping from the ceiling. Getting a little dry is a better option. If I had room I'd buy another similar size unit.

NOOO!!!  My humidifier puts out 2 to 3 GALLONS of water per day and it lucky to stay at 40% when it's really cold.  The sponges work because they are in a small enclosed space with no air exchange, so the moisture is trapped.  I don't bother with humidifying the cases.  The case does a good job of greatly reducing sudden temperature or humidity changes, which is what typically causes cracks.  Dropping from 40% to 25% in minutes could be a disaster!  But it will never get that low in a case, or it might take months if it isn't opened.