I have some RIR hens that are almost 2 years old... if i decide to butcher them, will they make good meat? i dont want to butcher them and have a bunch of tough chicken to eat... with the heritage breeds such as Plymouth rocks etc. when is the best time to butcher?
Accept disappointment.
If you want a tender bird, of any breed, you are almost two years too late. At that age, the only thing you can do is grind, season for sausage, and cure **or** stew/stock/pressure cook it.
With ANY BIRD of any breed, younger is better. The CornishX you get in the grocery store are between 2 and 3 months old. If you raised and butchered RIR at similar ages, they would be really tender. Small, but tender.
The older the bird, the more flavorful, and the less tender.
The more varied the diet, the more it can move around, the greater the flavor, and the less tender.
The older the bird, the less you want to rely on dry, high heat, fast cooking methods like broiling or baking, and the more you want to look to frying, smoking, braising, then stweing/stocking/sausaging. Its a sliding scale sort of thing. and comes down to personal preference as to where the cut off points are, but for most people, between 16 and 20 weeks, a bird has developed a good amount of "chew" and the bake-like methods are out.