I haven't had too many problems, certain times of year I do get sitting moisture, but I keep all my machines well oiled or greased and have covers over the beds-tables so it's not too bad.
the anvil gets wiped pretty often.
Now if there was no one ever in that shop for a year or so there would definitely be problems with rust. my biggest problem is with critters. I have four 10 x 12 roll up doors open all day every day and I'm out in the boonies in the woods, I have a lot of mud daubers and wasps cruising thru, along with spiders, lizards and the occasional but rare snake. as soon as I got my Cowboy 4500 I decided it wasn't staying in there and getting buggered up with insects. the mud daubers are actually the worst, trying to build nest in every little crevice they can find. but in the end....there's no where else I'd rather be.