You can still eat roosters that are 1+ years old, but as others say, they get though and chewy. We boil our roosters and then dice the meat across the grain. It works really well in soups, chili, and chicken salad.
Never let stock pot get to a boil. Simmer at best or your meat will be tough. Crock pots are easier to use but once you know your stock pot and stove maintaining a low simmer is easy enough.