These vouchers usually have an expiration date which is mostly 12 months. Once the coupons are expired, they become useless and can not be redeemed anymore. This is why it is important to use these vouchers for booking your flights or hotels. We have mentioned how you can use them to make Spirit Airlines reservations and save a lot of money.
https://www.debwan.com/blogs/167709/Book-a-Flight-with-a-Voucher-on-Spirit-Airlines