Typically 365 days from the event date, but that can vary from sports book to sports book. The back of the ticket will state the validity period. You can mail in winning tickets. The back of the ticket will provide mail in instructions.
Yes, you can mail winning tickets in. On my way out of Vegas I usually make a bet on a game I can either watch on the flight home or the day or two after. It helps ease the pain of the Vegas comedown after a trip.
Look on the back of your ticket. Yes, you can mail them in usually via registered mail, but what fun is that?
Pfft, don't risk forgetting to bring a winning ticket with you on the next trip. Mail it in as soon as you know it's a winner. I mail them in all the time. I don't bother with registered mail, just a regular envelope. Never had a problem and always get a check back within two weeks or less.