3 is the breadth. He could still write a paper providing a proof later Euclid found a more elegant proof which is now used in textbooks or stating his discovery of irrational numbers, a corollary of the Theorem for which he sacrificed a hundred bulls to the gods. A paper claiming the originality of the proof or a corollary, however, would be publishable. In short, the two versions should be different in substance. In principle, an author shouldn't be publishing the same result twice in different words.
Difference is a matter of degree.
Endnotes 1 . In this case, the publisher has to recover the cost from institutional subscribers. Publishers must draw a line somewhere but do not know where yet. However, the old style of displaying the referenced articles will remain for the time being. From personal correspondence.