It is absurd to think that the only way to tell if a poem is lasting is to wait and see if it lasts. The right reader of a good poem can tell the moment it strikes him that he has taken an immortal wound - that he will never get over it.
Omit needless words. Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts.