Walter Murch (The Conversations):

When you’re putting a scene together, the three key things you are deciding, over and over again, are: What shot shall I use? Where shall I begin it? Where shall I end it? An average film may have a thousand edits in it, so: three thousand decisions. But if you can answer those questions in the most interesting, complex, musical, dramatic way, the your film will be alive as it can be.

For me, the most rhythmically important decision of the three is the last: Where do you end the shot? You and it at the exact moment in which it has revealed everything that it’s going to reveal, in its fullness, without being over-ripe. If you end the shot too soon, you have the equivalent of youth cut off in its bloom. Its potential is unrealised. If you hold a shot too long, things tend to putrefy.