Briefly, you'll usually have about 30 days to send in your winning ticket (recommended via REGISTERED mail). Here is the pertinent paragraph in the Nevada gaming regulation:

22.080 Payment of winning wagers.
1. Except as otherwise provided in this subsection, books shall make payment on a winning
wager to the person who presents the patron’s copy of the betting ticket representing the wager.
A book need not make payment to a person who the book or an agent or employee of the book
knows is not the person to whom the patron’s copy was issued. A book shall not make payment
on a winning wager to a person who the book or its agent or employee knows or reasonably
should know is collecting the payment on behalf of another for monetary consideration or in
violation of federal law.
2. Presentment of the betting ticket and payment of the winning wager may be made at an
affiliated book provided that:
(a) An adequate accounting of the payment is kept for 5 years by both books; and
(b) The payout is properly included in the computation of gross revenue of the licensee that
initially accepted the wager.
3. Books shall honor winning betting tickets for 30 days after the conclusion of the event
wagered upon unless a longer period is established by the book. The book shall state the
redemption period on each betting ticket, in house rules and on notices conspicuously placed
about the licensed premises. Payment by mail may be made only after presentment of the betting
ticket, and must be made not later than 10 days after presentment.
4. A licensed race book shall determine the winners of or payouts on wagers on horse and
other animal races only with information the book receives from licensed disseminators pursuant
to Regulations 20 and 21.
(Adopted: 7/85. Effective: 9/1/85. Amended: 6/86; 7/87; 11/98; 9/05.)