Uh, umm, well . . . not in all cases. Putting it into OD all the time somewhat depends on your rear differential ratio. With my 2.73 gears in the back, my 4L60E rebuilder recommended that I put it into a manually selected D3 for around town, 45-50 MPH use. This prevents lugging my engine down to 1100 RPM all the time because the PCM wants to get the trans into OD quickly to save gas. In a manual D3, I still depart a stop sign in first gear, it shifts to second at a reasonable speed and RPM and then it proceeds to D3 at an optimal RPM and speed without burdening the engine down to 1100 RPM. This, in my rebuilder technician's mind, also keeps the strain lower on the 3-4 clutch pack friction disks - a well known weakness in the 4L60E. He also quickly mumbled something about higher apply pressure being applied to the forward sprag in D3 that I still don't completely understand. I'm a simple man when it comes to automatic transmissions and a good bit of that conversation might as well have been in the Martian language as far as my brain was concerned.
I only go to D4 OD on a road that requires a 55 MPH speed or higher. At 70 MPH, with those 2.73 diff gears and in D4 OD, I'm at 1800 RPM and sipping fuel at the 21 to 23 MPG rate like many modern vehicles. I can't smoke a tire (even if I wanted to) but I love those MPG numbers.
Rick