A notary public attests to the validity of the identity of the signature on a document rather than of the document itself, as stated by the Michigan Department of State Office of the Great Seal. There is no time limit on the validity of the signature.
The Michigan Department of State lists the duties of the notary as taking oaths and affirmations, witnessing signatures and taking acknowledgments. A notary may deal with a wide range of legal documents that require a notarized signature, but a notary does not necessarily need to know the content of each document. This is because the notary’s acceptance of the signature doesn’t equate to a statement that the document is legally binding or accurate. Therefore, any time constraints on the validity of a document need to be contained within the document and discussed with an attorney.