How do you expect to run 10 more miles at that pace when you haven't trained for it?
A long tempo of 15 miles IS "training for it". You do not have to run the full race distance in practice in order to perform well. That's not how physiology works.
True, but many posters here believe that because they read a few posts by Canova, they know how to train Americans (not themselves) to run 2:06