There was a (about 50 years old) mentally handicapped person that was in the Parade Magazine about 8 years ago that had documented over 1 million miles! Supposely all those miles on the same bike? I might have remembered the last part wrong. But he had a slew of worn out chain rings to prove the mileage and other documentation.
I pale in comparison to either with only just over 150,000 miles on the same bike.