question about humidy control

[Aaron Krister Johnson]

Hi,

I would love a consensus opinion regarding those little boxes that one 
installs to regulate local environmental humidity. I was told by one party to 
steer clear of them because they can cause rot, and that the best thing is to 
keep the piano in conditions that 'a person would find comfortable', i.e., 
"What you find comfortable, the piano will find comfortable" (caveat being 
direct sun exposure, etc.). I was also told by another party that I *should* 
have one to prevent the soundboard from cracking.

I have a rebuilt 1886 Steinway-B (7', rosewood finish, 19th century Victorian 
legs and scrollwork, etc.). I of course don't want to hurt it, and want to 
protect it.

What to believe? Is there an objective answer?

Thanks in advance,
Aaron.