How long has it been since Montag was normal in Fahrenheit 451?
I am not exactly sure of your question. Are you asking about Montag being like everyone else in the novel (unthinking, unfeeling)? That is apparently normal in the world that Montag occupies. People that think, feel, enjoy sunsets, and read are the abnormal ones. In chapter one Clarisse asks Montag how long he had been a fireman. He tells her ten years, since he was twenty. He also describes a time as a young child when the power failed and he and his mother sat by candlelight. He remembered similar feelings such as Clarisse described. So, to try to answer the question... Montag felt feelings that are normal to me and you when he was a child but not much more than that. He buried those feelings deep when he became a fireman. They were awakened when he met Clarisse. So, I guess he was normal most of his thirty years if normal is compared to most people in his world. He had a few touches in his life of feeling and thought but never to the extent as when he met Clarisse, hid books, and began his new life of thought and learning.