We cull layers at 2 1/2 yrs old and have cooked many. Think the oldest rooster I've done was about 18 mo. The older birds are always rich and flavorful.
In addition to pressure cooking and slow cooking, they're excellent for canning and stock making. Canned chicken is great to have around...quick meatpies, chicken and gravy, chicken and rice, quick soups or stews..etc, etc.
We also add pork, tomatoes, butter beans, potatoes onions and corn to make our own Brunswick Stew and can it every Fall. Those older flavorful birds make it delicious. It's a favorite quick meal for us on busy Winter days.