Does it heck!
There are a few conversations happening at the moment on various Blogs, about this very subject. An editor has apparently said that she wouldn't take on a new writer over the age of thirty-five!!! What? Is she living in cloud cuckoo land my dears? There are more older people than there are young - and that's rising my friends.
Writing transcends age. I bet a good writer could write a piece and nobody would be able to tell if that person is twenty five or sixty five. Now I could begin to say that mature people have more life experience, more mulled maturity, therefore are richer writers, but I won't, because to me it don't matter a fig. And a great big SADDO to those to whom it does matter.