Slabs are not airtight, so atmospheric conditions can affect the book. One of the more extreme examples may be slabs stored in certain safes that developed rusty staples.
Monitoring the humidity in your home or comic room is no more difficult than spending $10-$15 on a hygrometer at the hardware store. You can't just go by how it "feels," unless maybe you live in Arizona. And personally, I think a dehumidifier is a modest investment for your comic room if you have anything you'd like to keep in as good shape as possible.