Here's a question: Why is it so often assumed that the sonnets are autobiographical? Couldn't a series of poems be as fictional as a play? It strikes me that writing 154 sonnets on intensely personal subjects would be a very demanding experience. The fact that he didn't write any others (that we know of) could be taken as evidence in either direction, I suppose, but my own feeling is that the sonnets were another grounded and well-researched work of invention. We'll never know, of course - perhaps I'm wrong and there were some events from his life in these poems, but really it's somewhat beside the point. As they tell us all the way through, it's the lines on the page that last, and grow.