In my house we have or have recently sold steel bikes from the 40s, 60s, 70s, 80s, 90s, and 2000s. The ones from the 40s and 60s do have some rust, but they were both clearly left outside for years and years. The one from the 70s has some surface rust that could be taken care of with a steel pad if anyone liked that bike enough to bother. The ones from the 80s and 90s are completely clean.

I asked my husband about this yesterday because his new bike is CF. He loves that bike but he says he expects to trade it out for a custom steel frame in four or five years. CF is a lot better than it used to be, but I don't think anyone really knows how long CF frames are going to last. Earlier generations of CF frames are pretty much no longer on the road ... you see those ten-year-old Specialized Epics around, but that's about it.

(He wrecked his Giant last night, not badly but enough to put a ding on chain stay, and I am now a little worried about his continuing to ride it. On the other hand, he got hit by a car on a 12-year-old steel Allez this spring, and the frame is bent and unfixable, so the permanence of steel is also possibly a little exaggerated in some quarters.)