"You will eventually build up a resistance to salmonella, so if you've been drinking egg whites for years you are probably okay."
I doubt it. First, if you have not had illness from egg consumption, than most likely you have not come into contact with Salmonella. With no contact with the organism, there is no acquired immunity. Second, there are numerous strains of Salmonellae, not just one, so even if you possibly do build an immunity to one, there are others to take its place.