For the college track runner it is the ultimate day. For D3 runners to get a total time under an hour you have to be moderately competitive at every distance. I don't think D1 runners have the opportunity very often to run all three the same day because their meets are generally stretched over several days. Regardless of who you are it would not be easy. Of course if you want to push yourself why limit yourself to an hour? I kind of think that 52 minutes would be nearly impossible except for professional runners who rarely even run two races the same week. It's a unique opportunity to be able to run all three races the same day. For those of us moderately good D3 runners just trying to break an hour chances are no one would even notice outside of our team. It's also a waste of he next week because most likely you would be so sore after that that trying to throw down any workout that week or even a race the next weekend would probably suffer.
However, despite the sacrifice and stupidity of the 18k Superchallenge for any runner that completes it (that is all three the same day and less than an hour total time) let me know and show me the website with the results and I'll buy you a meal.