>Also 35 isn't 65. This is the prime age for most business people, artists, writers, etc. This is typically a professional and creative peak that lasts, at least, another decade or so. A person this age often has the drive and vitality of youth but the wisdom of someone older. Its no wonder so many great works are created by people around this age.
The age of 35 does represents an important milestone for many artists; it is the age when their creativity fades in both intensity and volume. What used to arrive almost spontaneously now requires hard and conscious works. This is the age where even Mozart needed to increasingly rely on sketches, and some of those who relied on their youthful facility, such as Rossini, simply quit composition altogether. On the other hand, someone like Beethoven who always struggled with composition from the beginning of his career probably did not notice this creative slump (Beethoven's crisis came later in his mid-40s).
This barrier to creativity that arrives in the mid-30s is especially evident in the Romantic artists, not just Wordsworth and Coleridge, but also Holderlin, Schlegel, Chateaubriand and Senancour. Charles Rosen speculates that is is because the inspiration for the Romantics was "drawn directly from memories of adolescence, and as these memories receded into the past their evocation became more and more artificial, or else the writer found himself with a fully developed manner and no content."[1] In this sense I do believe 35 is in some ways "old" as it represents a paradigm shift in one's approach to the creative arts, and maybe life itself.
[1] Romantic poets, Critics and Other Madmen, 1998