ld: Old fart speaking here:
I have my father-in-law's early 1960s Silvertone, solid mahogany uke that has survived nearly fifty years of neglect and abuse. No more. It now lives in a nice tweed case and in a humidity-controlled environment, as do my guitars. I have humidistats in three rooms of my house. I try to keep the humidity between 40% and 60% at all times. When it goes lower, all my solid instruments go in their cases with humidifiers. I have guitars that, even if I were to be able to get the insurance value on them, are irreplaceable and I'm a little bit of a fanatic about making sure they don't crack. That said, I have a sweet, sweet, sweet little vintage classical guitar (built in 1968) that has three scary cracks in the top and sounds great, so I'm not having those cracks repaired until they become problematic. I go without sleep in the winter trying to keep the humidity up in the house. Ignorance was bliss. Knowledge is stressful sometimes.
All solid instruments should be humidified if at all possible, but think about this: There are a lot of vintage instruments out there (Neil Young's Martin guitar that belonged to Hank Williams, for one) that were schlepped all over the country in non-air-conditioned cars (probably in the trunk or back seat, sometimes not even in a case), lived in conditions that were not even remotely climate-controlled, and which still sound great today and which fetch five figures or more on the open market.
You can get a very good humidistat at Walmart for around ten bucks. I have a top shelf, VERY accurate, analog humidistat from France that I paid an arm and a leg for and the ten buck Walmart humidistat consistently shows the same readings, so I'm confident that the Walmart humidistats are accurate. And, no, I'm not going to tell you what I paid for the French one. It's too embarrassing.
Obviously, we want to keep our treasured instruments from as much damage as we can. Sometimes, despite our best efforts, our best just isn't enough and we have to live/deal with the results. That's why we have luthiers/repairpersons who are competent to keep our babies alive and well. I'm fortunate that I live in Austin, TX and have access to the same luthier who keeps Willie's guitar "Trigger" functioning. His prices are competitive and I figure if he can keep Trigger going, he can definitely deal with anything I can throw at him.
:music: