The last stretch of any task costs far more than the first. Once you know that, you can decide where near perfect is worth the price and where it is not. Bunk cleanup has a point past which nobody gains anything. Filling your final staff openings does not. The skill is telling those two situations apart before you spend the hour.
This is the short version. The full lesson, with the story behind it, is in the book.
Take The Summer Camp MBA with you, or get the field notes by email while you work through the lessons here.