Where to draw the line?

When is a book finished? Does this seem like a silly question? It certainly vexes me, and I suspect it vexes some other authors too.

A case in point. I've just finished work on The Hanging Wood, the fifth Lake District Mystery – hurrah! It is in good enough shape for it to be sent to my agent for assessment. (She earlier looked at a portion of the first draft.) But within an hour of my sending it to her, another idea occurred to me. A small point which I felt would improve the book.

This happens all the time. I keep thinking of ways to make a book better. Worst of all, when I am unwise enough to re-read my early efforts, I have lots of ideas as to how I could have improved them! But the fact is, you have to draw a line somewhere. There is some scope, though limited, to revise bits during the publishing process. But in due course, you have to say, 'That is it.'

My ideal, I guess, would in theory be to have enough time to put a manuscript away for a few weeks, look at it again with fresh eyes, then put it away again, revise again, and so on, perhaps half a dozen times. But this is not possible. Deadlines keep looming, other projects crop up. Making any artistic work does involve some element of selection, and sooner or later every creative artist, however humble their efforts, has to say to himself or herself that it's time to let go. Not easy, though!