I just read that about the VLCC (after I did the search as appropriately admonished) - the required distance is whatever you think is "very long". There were some on there doing 10 miles each way. Personally I do 18 - 24 miles just about every day as part of my training, so doing the additional 26 miles would be doubling my current daily mileage... so I think about 52 miles per day as "very long"