The U.S.P.T.O. doesn't specify the last day you can file a request under QPIDS, but Question 12 of the FAQ says the request can't be submitted on or after the day the patent issues, so presumably you can submit the QPIDS request any time before the issue date of the patent.
The FAQs can be found here:
www.uspto.gov/patent/initiatives/quick-path-information-disclosure-statement-qpids
The FAQs can be found here:
www.uspto.gov/patent/initiatives/quick-path-information-disclosure-statement-qpids