IMHO, you should shoot at a target only so long as you can shoot good shots. Before and after that you should shoot a blank bale, first to warm up and improve your form, then to build endurance & improve form.
There is an old saying that "Practice doesn't make perfect, Perfect practice makes perfect".
The practical application to shooting is to only shoot at a target as long as you can manage the best form of which you are capable.
But what if that's only a few arrows? You still need to build strength and endurance for whatever game you plan to compete in. That is where the blank bale comes in. You can also concentrate on each part of your form without worrying about trying to hit a specific spot.
There seem to be two parts of practice that are effective to building good form. First is the first 10 to 15 arrows. You have to know all the parts and pieces of your shot to get these right. The second is when you are tired. If you can keep good form when your muscles are tired, you are more deeply ingraining good form into your subconscious.
Just my opinion,