You can use the LUV voucher on a flight booking(s) for anybody and use two of them for the same person if you wanted to. .....
If you buy Basic with the voucher, the expiration is shortened to 6 months and it's irreversible.
Thanks for clarifying and for new info - it puzzled me and AI gave the following clarification:
Southwest LUV Vouchers typically expire one year after issuance. However, if you use a LUV Voucher to book a Basic fare ticket and then cancel that flight, the resulting flight credit will expire in 6 months from the date of booking, not one year. This 6-month expiration is shorter and applies specifically to the Basic fare class. Moreover, this expiration shortening is irreversible, meaning once the voucher is used for a Basic fare and converted into a flight credit with the 6-month expiration, you cannot extend or revert it back to the original 1-year LUV Voucher expiration period.