I'll tell you what I tell everyone about humidity (I don't expect everyone to agree with me) but it's what I found works. I keep my humidity at around 40% all the time, EXCEPT when they are in shed. At which point I bump it up to 60-70%.

Why?

I find high humidity can lead to RI's - I was keeping my guys at 60 - 80% all the time for the first year I got them and I had to keep fighting off RI's. Switched to 40% and I haven't had an RI in 4 years...

Just my experience, take from that what you will.