I use sphagnum moss in Emily's humid hide (aka margarine tub with moss in it ) I've never had any problems with it and just buy more when it gets icky - it is sometimes used to poo in!! so I check that.
I spray it every day and when she's going into shed I spray it like 2-3 times a day and she does sometimes go inside it and sink under the moss. She's just had a lovely shed too