300 miles, on the double/triple/quad century course in Litchfield, IL in 1984 (when I was 34 years old). My time was 22 hours, 45 min. and I was mostly dead at the finish.
Next longest was 276 miles, St. Louis to KC MO on the first day of BAM (Bicycle Across Missouri) in '85. My riding partner (Peggy Davis) and I finished the 566 miles in just over 56 hours.
Probably something similar on P-B-P in '91, but I'd have to look at my control-check book to be sure.
Rick / OCRR