My Trek 660 has roughly 155,000 miles give or take a 2,000 miles. And I still ride it as my main bike. The Mercian has only about 600 miles on it, but this one I'm saving for tours; and the Giant has roughly 18,000 miles, 8,000 of those miles are on the trainer. All 3 bikes were purchased new.

By the way, the older Trek chain is the older style wide chain not your newer narrower chain, these wider chains typically last about 13,000 to 18,000 miles.

As far as a steel frame "failing" thats mostly crap! Sheldon Brown rode on an old 1916 Mead Ranger gas pipe frame bicycle a lot to work. I have a friend (205 pounds) who has well over 300,000 miles of mostly loaded touring on his steel touring bike and it's still going strong. Another friend who got involved in touring about 8 years ago, another big fellow at 225, has a Rivendell with now over 80,000 miles. Another friend with a 85 LeTour that he has ridden everyday (he can't drive) and he's estimated his mileage to be about 425,000 miles. There was a guy in the Parade mag some years back with documented miles of over 1 million miles! In otherwords a steel frame failing from just wearing out after only 30,000 miles is obsurd.