Large Yard Focal Points
When you are lucky enough to have a large yard, by all means use every bit it in the site plan. Even if you don't physically use some areas, they can still be a high visual priority. Why? Because it's what you see that defines the sense of space, not necessarily how big it actually is.
Your designer knows how to create a landscape that draws your eye out to the furthest points of the space. This is achieved by setting one or more major viewpoints terminated by a visual payoff, a delicious reward for seeking what lies beyond. This viewpoint should be large enough to speak to you over this distance, and therefore it must be in scale. A large yard can easily utilize life-size figurative sculpture. A large flowering tree at the opposite end of the yard becomes the seasonal highlight of the spring garden when viewed through windows, or observed as a focal point from outdoor living spaces.
A different approach is to create a number of these points of interest at varying distances. If each one is terminated by a sizable accent plant, one may bloom early in spring to carry the landscape when it's still partially dormant. Another can become the essential eye-catcher during the blooming lull of midsummer. The third might provide fiery autumn hues. Variation through the seasons gives the landscape an ever changing dynamic, so it will never become visually monotonous.