Yup, depends on the weather. And to some extent, the time of year. Later in the season they will stay later.
Figure on the first ones landing before you can see them. They don't always, but often enough to make being in the blind before you can see the field well worth it.
Took that photo 15 minutes after the first birds had landed. There wasn't enough light to photograph them silhouetted against the sky for the first few and I couldn't even see the birds in the field yet when this flock came in.