Saw an ad a couple of nights ago for Fabreze Auto freshener. Up till now, when the rig starts to get that "funky, sitting in the driveway smell" I mix up a scoop of Oxiclean with a quart of water, and pour it into the storage tanks, that helps a lot.
Mine had a funky smell in it when I bought it last fall, but I think it was mostly from the funky smelling previous owner, and it is over 30 years old as well.
I had to get out the febreeze on the carpet in the bedroom and all the cushions, but what helped the most was getting out the lemmon scented oil soap and cleaning all the wood. Then I got a vanilla smell odor neutralizer air freshioner in it and the funk finaly went completly away.
I'm using my RV as an office (I'm typing this sitting in the RV in front of the house) since my father in law is up for a visit and is sleeping in my office, so the inside of mine is staying somewhat heated and not stale in the winter to regain the funky smell of an old rig.