Beef stock requires more than just two hours because of the size and thickness of the bones. Chicken stock does not. The bones are smaller and more porous, and give up their content and flavor much faster.
You can also add chicken bouillon cubes to make it really tasty
Chicken stock is chicken-vegetable soup with all of the bones and vegetable solids sifted out after it's finished cooking. From beginning to end I make mine in one to two hours. Any longer than that and the flavor begins to go funky. Within the first hour or so the vegetable flavors still taste fresh and the chicken flavor is distinct.