Making the most out of stock I came across a page (http://www.traditional-foods.com/bone-broth/) where the author used the same beef bone 12 times to make stock*. It got me wondering: when I make stock, am I leaving behind that much more flavor in a bone, or did she do something wrong? What should I do to extract the most amount of flavor out of my bones?


Use a higher bone/water ratio? Does the water saturate with the contents?
Cook it for a longer time? 
Use a different cooking method? She uses a crock pot, I believe. 


I use a 10qt pressure cooker for my stock, and I usually cover my ingredients with water plus an inch as a rough guide. I also plan on reducing the stock afterwards, so if more water doesn't help with extraction, I don't want to waste time boiling it all away in the end. 

*Since she calls it bone-broth, I'm guessing she's from the Nourishing Traditions camp where they are interested in extracting nutrients, etc. from the bone. I don't know if getting extra gelatin out of a bone means more flavor was left behind originally.
From a culinary viewpoint, there is little to no reason to use bones more than once in making stock.  Even the author of the article you reference indicates the first go is the one that tastes best.  

To maximize the quality of your stock:


Use good clean or filtered water; add hot water as the stock reduces over time to keep the level above that of the bones
Use good bones, chopped with a cleaver to reasonable sizes (a few inches)
Optionally roast the bones prior to stock making for a deeper, browner flavor
Skim the scum in the first part of the stock making process (obviously not an option in a pressure cooker)
For a more clear stock, don't allow it it boil, but rather than let it go at a slow simmer (again, not in your control with a pressure cooker)
Simmer it long enough for reasonably full extraction, which will leave the bones either bendy (more in the case of poultry or long bones) or somewhat fragile
Include good quality vegetables for flavor
Don't salt the stock, as during reduction it can concentrate and become overwhelming


In other words, apply basic cooking common sense and you will have a good outcome.