I worked in a bike shop for 4 years and have never heard of failure or rusting through on any newer bike. The only time I have ever seen rust on a newer frame at all was if they took a nasty digger and put a huge gash in the frame or somthing. I've been riding on steel for 8 years now and haven't done a thing to my bike after wet rides and havn't had any problems at all. Your drivetrain is the only thing that I would worry about! Keep it well lubed and you won't have any problems.