We've had our coach two years now. They've remained free of any corrosion over that time. This year I did spray the posts with a battery cleaner from the auto store. When dry I sprayed with a corrosion preventer. That has a red die of some kind in it that will change color if there's corrosion present. Didn't see any signs.
I preferred not to disconnect everything to clean if a problem wasn't apparent. I just tightened all the connections a bit. Some of the battery clamp straps loosened a bit over time. Its a good thing to check those too as if the battery can move slightly while driving it'll loosen the battery connections.
I installed ( really easy) the battery watering system. You can water them all at once from the outside of your RV.
http://www.janwp.com/mm5/merchant.mvc