Southwest LUV Voucher - Terms and Conditions
Southwest LUV Vouchers and air fare paid with Southwest LUV Vouchers are subject to the applicable incorporated terms, Contract of Carriage, and rules and regulations of Southwest Airlines.
Southwest LUV Vouchers are valid as a form of payment toward future air fare only on Southwest Airlines through southwest.com, toll-free Reservations at 1 800 I FLY SWA (1 800 435-9792), or at any Southwest Airlines Ticket Counter.
Southwest LUV Vouchers must be redeemed and all travel completed by the expiration date indicated. If applied in conjunction with any other accepted form(s) of payment, the earliest expiration date of all payments applies. Validity of Southwest LUV Vouchers will not be extended and any unused value will be forfeited upon expiration.
Southwest LUV Vouchers are not redeemable as payment toward U.S. Government-imposed segment fees, Passenger Facility Charges, or September 11th Security Fees or as payment toward miscellaneous charges, Southwest Airlines Vacations packages, or travel either wholly or in part on other air carriers.
Southwest LUV Vouchers and travel issued in exchange for Southwest LUV Vouchers have no cash value and cannot be exchanged for cash or other monetary consideration. Southwest LUV Vouchers will not be replaced if lost, stolen, or destroyed.
To redeem a Southwest LUV Voucher, purchaser must have a Southwest LUV Voucher number and associated Security Code. If balance remains after redemption, please retain this Southwest LUV Voucher number and security code for future use.
Southwest LUV Vouchers are VOID if sold, altered, purchased, brokered, and/or bartered.
https://www.southwest.com/luv_voucher/voucher_terms_conditions.html
I wouldn't suggest buying them. lol