Every book takes me from 35 to 41 days to write. I don't...

Every book takes me from 35 to 41 days to write. I don't know why that is. I've tried to get it down to 30 or 31, depending on the length of the month, but it won't work. I don't drink while I'm writing because it fuddles my logical processes, but when I finish a book I go down to the kitchen and pour myself a big belt.