We have that many cats and our house doesn't smell bad either. It's actually not hard to keep your house smelling nice with cats. It's much harder with dogs since most dogs smell, especially if they've just been outside.
With the exception that their cats prowl the place (especially Bane) like lions searching for savannah prey, you could not tell they have cats, at all. Their house is so clean, you would think that someone inside has some serious OCD issues.