Unlacquered brass will definitely tarnish up quicky, but I think that's part of the appeal to those who like the look. I think that extra care should be taken to keep the instrument clean and dry when the brass is bare - and I don't necessarily mean polishing it all the time. Certainly, pitting and other corrosive activity is going to be more prevalent when the finish is not protected from the acids and oils in your skin and sweat. Doesn't mean your horn will look like swiss cheese in 5 years or anything - just practice good sax hygeine and the instrument should hold up similar to any other.