Hmm. I think the materials of the finish applied do make a difference. UV cured polyester, lacquer(s), oils (tru-oil) have different benefits. The UV cured polyester seems to stand up pretty well to sweat, lacquer and oils to a lesser degree. However, UV cured polyester is tough to repair. Oils are pretty easy to repair. One can also use wax on an oil finish to help reduce sweat effects.
Nothing protects a uke from temp, humidity extremes, except avoiding those.
However, I think the oils, as penetrating substance have less of a 'film' are thus less susceptable to cracking from temperature variations.
Just my observation, based on limited data.