My sewing cave has been in the basement of my home for over 17 years now without a problem. I got moved to the basement when we found out we were having our son. When we first moved in we didn't use a dehumidifier and had problems with stuff, so we have run a dehumidifier in the basement in an on 4 hours off 4 hours ever since. I keep two computerized machines, books, fabric, yarn and lots of important stuff with no problem.
I refer to it as my sewing cave and keep teasing my son and telling him that I expect to get that sewing room back soon so he better plan on college and not coming back because I am laying claim to that territory.