I have been reading Claire Tomalin's bicentennial biography of Charles Dickens – the latest in a long line that begins with The Life of Charles Dickens by the novelist's friend and adviser John Forster, and includes important studies by Peter Ackroyd, Michael Slater and, most recently, Becoming Dickens by Robert Douglas Fairhurst.

The thing I always take away from reading about the Inimitable, as he styled himself (half-joking), is his prodigious energy and his Victorian capacity for sheer hard work. Reviews, letters, petitions, journalism, stories, plays, scraps of poetry, more letters on myriad topics (from interior decor to prison reform), and finally of course the 14 great novels themselves.

But then, as you go deeper into Tomalin, you discover that Dickens, in his prime, used to compress his literary energies into five hours, roughly 9am to 2pm, after which he would walk incessantly, and put his mind into neutral. He might return to what he'd written in the morning later in the evening, but those five hours held the key to his output. Which raises the question: what's the best time of day to write? and its corollary: how many hours are necessary?

Some writers (Dickens among them) are larks. Others – more nocturnal – are owls. Robert Frost, whose remote Vermont cabin I visited recently in company with his biographer Jay Parini, never started work till the afternoon, and often stayed up till two or three in the morning, not rising until midday, or even later. Proust, famously, worked night and day in a cork-lined room. I remember reading somewhere that Raymond Chandler observed that it was impossible to write well for more than four hours a day. What do you do in the afternoon?

There's also the question of how long it might take to complete a novel. Here, you encounter literary legends. Faulkner claimed to have completed As I Lay Dying in six weeks. In the mid-1930s, PG Wodehouse, who wrote fast once he had the mechanics of his plots straight, polished off the last 10,000 words of Very Good, Jeeves! in a single day. In his autobiography, A Sort of Life, Graham Greene describes writing Stamboul Train on benzedrine, to pay the bills, working against the clock. Further back, Samuel Johnson wrote Rasselas, which is short, in a fortnight to defray the expenses of his mother's funeral. Or so it's said.

More usually, a 60-70,000 word novel seems to take at least a year to complete, allowing for two or three drafts, although often the first, rough outline can get written in a matter of weeks. The strange truth about a lot of fiction is that the dominant moments that animate an entire novel can occur to the writer in a matter of minutes. After that, in the words of one New Zealand writer I recall with affection, "it's just typing".

Dickens, of course, lived in the golden age of the typesetter. His strong, decisive manuscripts (he boasted a very clear hand) were swiftly transformed into galley proofs, for endless re-writing, the really time-consuming part of the process. The revision is the bit that many writers really enjoy, once the heavy lifting of the first draft is done.