40 days.

"The main reason that artists don't willingly describe or explain what they produce is, however, that the minute they do so they' ve admitted failure . Words are proof that the vision they had is not, in the opinion of some at least, fully there in the picture. Characterizing in words that they thought they'd shown is an acknowledgment that the photograph is unclear - that its not art."

Robert Adams, Why People Photograph (pag 33.)