Since many fig trees have suffered winter damage over their lives, how do determine the age?  Is it by the root?

Also, I have read many times that the older the tree is, the better the figs are.  My question is, again, is that determined by root age or trunk/branch age?

Most people determine the age by asking the owner  :)   That said, the diameter of the main trunk gives you some indication.  You don't get a 5" trunk in 2 years.  A bush form will probably have narrower trunks than a tree form of the same age so there's no absolutes. 

As far as fruit quality, fruit only develop on wood less than 2 years old so branch age isn't the issue  :)  I would guess root and trunk age figure in to it.

Let me clarify.  Take my mom's tree for instance.  It has been planted there for 80+ years, but it has had damage over the years so the trunk(s) do not have the caliper of a tree that has not suffered.  Is the age still considered to be 80+ because the roots are, or would it be considered a younger tree since the trunks(s) are?

Since, fruit develops on new growth, how do the figs get better with age?  Is it then based more on the age and size of the roots and their ability to feed the tree and process the nutrients because there is more mass to do the job?

     JoAnn, I think you just gave yourself the answer to the question.

I think your right!!  See what happens when you talk to yourself!  ;) ;)

Problem is I don't listen to myself when I talk to myself  : )