I am not aware of any law that requires an individual to retain copies of court documents for a certain length of time. You have to use your judgment. You have not described the nature or resolution of the prior court action, so it is difficult to give you any concrete advice. As a general rule, I would keep anything that shows you are no longer responsible for anything. For example, if a plaintiff obtained a monetary judgment against you which you paid in full, then I would keep a copy of the satisfaction of judgment for a period of time.