The human body prefers the same humidity levels as solid wood ukuleles, so if your instruments stay mostly in the same room, and it's a room you spend a lot of time in also, it may be worthwhile to just humidify the room. But I don't live in a place where the air gets extremely dry in winter, so I can usually maintain 35%+ even in winter, with just some plants and myself in the room, which I feel is just fine. It's only when I leave the window open for an hour straight or don't close the door (into the hallway) that it may drop to 25-30%, which is probably still fine as long as it's not a long term condition.
Nevertheless, this is one reason why I bought Kiwaya/Famous laminate soprano and a guitar with only a solid top, and why I keep looking at Blackbird instruments. Worrying about the instruments takes some fun out of the experience.