If you have a "flight credit" that is about to expire, if at all possible, use it before it expires. Reservation agents are not expected to know about the rules, so they can't warn you, as follows. If the flight credit expires, it is true you can get a "voucher" that gives you another 6 months, but not if flight credit is less than $100. Furthermore, even if your flight credit is more than $100, the amount of the voucher that gives you 6 more months will be reduced by $100.
