My personal longest ride is 710 miles in a day - Colorado Springs to Oklahoma City. That is my choice, I'm sure I could make 1000 but not real sure about day after day of it.
Iron Butt Association has several certificates they offer - at a price - on this site:
http://www.ironbutt.com/ridecerts/
I have 3 friends who are about 10 days from embarking on a 100CCC ride, which is coast to coast and back in the USA in 100 hours or less.
I count among my friends about a dozen who have one or more of the various IBA certificates.
My thinking is even if I did accomplish any of the rides as described I'll be damned if I would pay IBA for bragging rights. The cost of a certificate would buy the gas for almost 1000 miles.