If there is a physical lottery in our country, it will expire, and this depends on what kind of lottery game you are joining; they range from 3 days up to 1 month, and after that, you'll lose your winnings if you haven't claimed them as that is their agreement. But online, I am not really aware of it, but I am not sure why you will be leaving your winnings or, like, forgetting it. I mean, you can check it on a daily basis, like every minute, or they are also sending you emails to make sure that you won.