My longest 1 day solo ride was 152 miles in 2009 from Pittsburgh to Cleveland, 9:20 pedaling time. My longest ride before that was 30 miles but, I was commuting 100-160 miles a week and I like endurance challenges which is why I was comfortable doing it.
I plan on doing a solo double century in July or August and will also be doing this ride for the 3rd year in a row in a few weeks.