Happy Tolkien Day!
letter 62 in process of writing part of Two Towers 1944 to Christopher Tolkien
"I read my second chapter. Passage of the Dead Marshes, to Lewis and Williams on Wed. morning. It was approved. I have now nearly done a third: Gates of the Land of Shadow. But this story takes me in charge, and I have already taken three chapters over what was meant to be one! And I have neglected too many things to do it. I am just enmeshed in it now, and have to wrench my mind away to tackle exam paper proofs, and lectures."
We know that he wrote LotR for 12 years, didn't he?