I save an eligible ticket, put it somewhere safe, and then almost miss the entry date. Safe was too safe I guess. Do you enter them right away or keep a weekly pile? Please name the state too because every program seems different.
Enter the code when you decide to use it instead of keeping a long pile. The exact deadline belongs to that state's promotion, not to scratch tickets in general. Check the game number, official end-of-game page, final entry date, location/residency rule and whether the original ticket must be kept.
For a concrete example, California says Scratchers 2nd Chance codes expire 180 days after that game's official end date, entries must be submitted within California and the account needs a valid California address. Another state can use a different window and eligibility rule.