Share 'What Are the Ideals to Aim for in a symphony ?'

Nobody has ever written a text book explaining how to write a symphony. All we have is a legacy of symphonies that over the years, some of which are widely regarded as being "great". So what do you think constitutes the ideal symphony ? I'm attempting to write my own, and for an exercise in self criticism, I came up with the following factors: 1. Musical interest and originality sustained throu…