I think this depends mostly on where you live. "Up Nort" it gets so dry that your skin cracks and I know no-one to worry about moisture when they store their rigs.
What we do when we put our 5'ver away down south for the summer to combat problems with moisture is four things.
- Put crush newspaper in the cabinets
- Put pans of kitty litter out
- Put pans of charcoal out
- Put two big tubs of Damp Rid (buy at WalMart in the RV section) out.
When we show up in the fall the 5'ver smells, looks, and feels like the day we put it into storage.