I keep a humidifier in the case, even with my all laminate uke. The neck and fret board need humidity. I didn't humidify once and got sharp fret ends aka "fret sprout." With a solid top, I'd humidify if you live in a dry climate, or use forced air heat in winter.
Here's my single data point: I've had a solid top uke hanging on the wall for a couple years without issue. The humidity gauge next to it occasionally gets down to the low end of 20% in the winter. I'm in North Carolina (Raleigh area).
A solid wood top requires the exact same care as an all solid wood instrument. Even laminates, although a bit more resiliant, will suffer from dryness (sharp frets to begin with). Wooden instruments are actually similar to human beings: best for them is a relative humidity of about 40-55 percent.
I have a solid top with laminated bod and an all solid. I have never had any problem, but I moniter the humidity in the winter. here. It normally stays from about 45 through 35 in my house in winter. When it goes below 40 I humidify. It is easy and doesnt take much effort. Better safe than sorry I feel