Are Steam Humidifiers worth it?

I live on the MN/IA boarder where our summers are extremely humid, and our winters are brutally dry. We currently run between 3 or 4 portable humidifiers in our house in the winter but our humidity in the house is hanging around 35%.

Our furnace and AC are on their last legs. The house is 20 years old, and it's the originals to the unit.

With that being said, is it a good idea to add in a steam humidifier to our furnace and just not run it half the year?

Any input helps. Thanks, all.