Moisture isn't really the issue with range hoods, more over, it's the oil you have to deal with. With oil, you're not going to see the rusting on range hoods.
Long life range hoods are not common. I've seen high end brands and low end brands and all experience their problems. Cousin's Fisher & Pakyl range hood (budget model) had it's control board go up in smoke (less than 3 years). My aunt recessed fixture range hood had it's motor pack up ($800 replacement cost on motor). Overall, buy on function and ease of cleaning rather than buy on looks.