We have been eating bone broth each day for well over a year. The last few months we have been cooking it for 48 hours. The bones just crumble apart after this length of cooking. We stopped making it for the summer months though as it was too hot in the house.
There are a few local organic farmers who sell bones as well as all other cuts of meat. Just phone around or google farmers in your area.
Adding chicken feet, animal joints, and knuckles to a bone broth will increase the amount of collagen available.
Considering we are taking supplements, eating a paleo diet and eating lots of bone broth it is difficult to say which has had the greatest impact. Probably a combination of everything but the bone broth is super nutritious.