They do have expiration dates. All of the casino promotions have what are called validity periods with them. The information can always be found under the terms and conditions. It is important that before you claim any casino bonuses, you read the terms first. This will help you so that you are aware of what those bonus validity periods are to make sure that you use all of them within the time frame. If you do not do so, you will forfeit the bonus balance and the amounts you have already won. This is something that casinos do in order to get players to use up those bonuses quickly and getting them to start wagering actual money.