What is the statute of limitations in your state? That might guide it.
Some states have limited terms of potential liability. In my state, I think (but I'm not sure) it's 2 years from the date of "injury." But you have another 3-4 years to "discover" an unknown injury before it starts the 2 year clock again. That is, if you discover a mistake was made after 3 years, you can still sue. But if you knew about it 3 years before, you can't sue for that anymore. And I think if it's more than 6 years, you can't sue at all (excepting cases of fraud or something). Every state is different - some may be unlimited, some may be more restrictive.
These laws change in the even of outright fraud though, and sometimes limits don't exist for pediatric cases or something.
These laws are also always subject to change with whoever controls the judiciary machinery in the state though.