River Cottage

the us fda say that as long as its properly cold , it keeps indefinitely, especially if its ingredients for stock.
http://www.fsis.usda.gov/FACTSheets/Focus_On_Freezing/index.asp

Hello,

We kill about 50 chickens in September. Obviously I can't use all the carcasses at once. So they go in the freezer, for up to one year. After that point, they are not necessarily bad - after all, you will cook them for several hours, so what bacteria can survive? - but I make it a good habbit to empty the freezers once a year so they can be defrosted and cleaned.
Other bones, such as sheep, goat and oxtail also routinely go into the freezer. I don't even put a date on these bags because we're sure to eat everything before the next load comes in.
When I make stock and it is too much, I sometimes freeze it again, even if it was made from bones that were already frozen once. When you heat it, you boil it anyway, so I think nothing can happen to you. At least, nothing ever happened to us ;-)
Sometimes it happens that if meat is frozen for a long time, like +6 months, in inappropriate bags (for some parts I have to use clean, unused garbage bags because they are too big for our max 6l freezer bags), that the meat gets frost damage. But it is still edible, the damage is only a beauty spot. Of course, I'm not a nutrition specialist and I never had my meat, bones or stock analyzed, so maybe it degenrates a bit from freezing, but I'm quite sure it's not toxic.

Hope this helps,

Machtelt.