At what age is an authors best work completed?

I have been pondering this question lately: Will each of my novels get better and better? Of course, with that question comes the comparison to other writers, artists, sculptors, architects, composers. When did their best work appear in their lives? With each I can point to their masterpiece. Most produced other works after that point but they did not rise to the level of their masterpiece.

Christopher Ingraham of the Washington Post wrote an article entitled, "Writers, artists and composers tend to peak in their late 30s and early 40s." He compares this to the game of life.

Jim Michener was once quoted as saying no American author had produced a great book after age 80 and he did not suppose he would be the first. You can count several masterpieces in his middle age, but not his early ones nor his later ones. A friend disagrees with me as I think Centennial, is his masterpiece. Andrew Kaplan thinks it is The Source.

Can writing be an inclined plane, each successive work besting the one behind? Can you eat right, sleep and work out and dream big dreams and do that? Ingraham says "...on average, Nobel Prize-winning writers produce their best work at age 45. Painters peak at age 42. And classical composers produce their most popular works at age 39."

I'm closing in on twice the average age of Nobel Prizewinners yet I feel vibrant and that what I have to write is meaningful. So...when did you do your best work?