The Roberts Compact Audax frame I bought to start my Audax career has now logged 100,000km. Before there are cries of "Trigger's Broom", the frame is original, although it's had a couple of repairs due to encounters with a bollard and a car in different incidents. The forks were replaced after the second incident. The Tubus rack is also original, but its on its second pair of handlebars and a long while ago had a conversion from Campag to Shimano. It's completed 2xPBP, the Mille Alba, and the West Highland 1000, as well as a fair number of 300s, 400s, and 600s over the years. After the second repair it had a respray and ended up a rather anaemic yellow, but a complete rebuild from Argos Racing Cycles restored it to its resplendent Flam Yellow. It's in its 21-st year, but still beautiful to ride, so I guess it will keep in circulation with a new goal of 100,000 miles.
I am sure there are much more veteran frames out there and would be interested to hear their tales.